Projection exposure method and apparatus

ABSTRACT

A projection exposure apparatus and method that includes an illumination system and a projection system. The illumination system may include a plurality of optical integrators that form different secondary light sources. The illumination system illuminates the pattern with light from a secondary light source selected based on the pattern. The projection system projects an image of the pattern on a predetermined plane. The projection exposure apparatus may also include a light shielding device having a cross-like portion extending in first and second directions defined by the components of the pattern. Even further, the projection exposure apparatus may include four off-axis secondary light sources where a ratio of a numerical aperture of a light beam from each of the four secondary light sources to a numerical aperture of the projection optical system is substantially 0.1 through 0.3.

This application is a Divisional of application Ser. No. 08/376,676filed Jan. 20, 1995, which in turn is a Continuation of application Ser.No. 08/122,318 filed Sep. 17, 1993, now abandoned, which in turn is aContinuation of application Ser. No. 07/791,138 filed Nov. 13, 1991, nowabandoned. In addition, application Ser. No. 08/376,676 is aContinuation-In-Part of application Ser. No. 08/257,956 filed Jun. 10,1994, now U.S. Pat. No. 5,638,211 which in turn is a Continuation ofapplication Ser. No. 08/101,674 filed Aug. 4, 1993, now abandoned, whichin turn is a Continuation of application Ser. No. 07/847,030 filed Apr.15, 1992, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed generally to an exposure method and anexposure apparatus, and more particularly, to a projection exposuremethod and a projection exposure apparatus which are employed in alithography process for liquid crystal elements and semiconductor memorycells having regular hyperfine patterns.

2. Related Background Art

A method of transferring mask patterns on a substrate typically by thephotolithography method is adopted in manufacturing semiconductormemories and liquid crystal elements. In this case, the illuminationlight such as ultra-violet rays for exposure strikes on the substratehaving its surface formed with a photosensitive resist layer through amask formed with the mask patterns. The mask patterns are therebyphoto-transferred on the substrate.

The typical hyperfine mask patterns of the semiconductor memory and theliquid crystal element can be conceived as regular grating patternsarrayed vertically or horizontally at equal spacings. Formed, in otherwords, in the densest pattern region in this type of mask patterns arethe grating patterns in which equally-spaced transparent lines andopaque lines, formable on the substrate, for attaining the minimum linewidth are arrayed alternately in X and/or Y directions. On the otherhand, the patterns having a relatively moderate degree of fineness areformed in other regions. In any case, the oblique patterns areexceptional.

Besides, a typical material for the photosensitive resist exhibits anon-linear photosensitive property. A chemical variation thereof quicklyadvances on giving an acceptance quantity greater than a certain level.If smaller than this level, however, no chemical variation advances.Hence, there exists a background wherein if a difference in lightquantity between a light portion and a shade portion is sufficientlysecured with respect to a mask pattern projected image on the substrate,a desired resist image according to the mask patterns can be obtainedeven when a boundary contrast between the light portion and the shadeportion is somewhat low.

In recent years, a projection exposure apparatus such as a stepper, etc.for transferring the mask pattern on the substrate by reductiveprojection has been often employed with a hyperfiner patternconstruction of the semiconductor memory and the liquid crystal element.Special ultra-violet rays having a shorter wavelength and narrowerwavelength distributing width are employed as illumination light forexposure. The reason why the wavelength distribution width is hereinnarrowed lies in a purpose for eliminating a deterioration in quantityof the projected image due to a chromatic aberration of the projectionoptical system of the projection exposure apparatus. The reason why theshorter wavelength is selected lies in a purpose for improving thecontrast of the projected image. Shortening of the wavelength of theillumination light induces a limit in terms of constraints of lensmaterials and resist materials in addition to the fact that noappropriate light source exists for the much hyperfiner mask patternsrequired, e.g., for the projection exposure of line widths on thesubmicron order. This is the real situation.

In the hyperfine mask patterns, a required value of the patternresolution line width is approximate to the wavelength of theillumination light. Hence, it is impossible to ignore influences ofdiffracted light generated when the illumination light penetrates themask patterns. It is also difficult to secure a sufficientlight-and-shade contrast of the mask pattern projected image on thesubstrate. In particular, the light-and-shade contrast at the patternline edges remarkably declines.

More specifically, respective diffracted light components, a 0th-orderdiffracted light component, (±) primary diffracted light components andthose greater than (±) secondary diffracted light components that aregenerated at respective points on the mask patterns due to theillumination light incident on the mask from above pass through theprojection optical system. These light components are converged again atthe respective points on the substrate conjugate these points, therebyforming the image. However, the (±) primary diffracted light componentsand those larger than the (±) secondary diffracted light components havea much larger diffraction angle than that of the 0th-order diffractedlight component with respect to the hyperfiner mask patterns and aretherefore incident on the substrate at a shallower angle. As a result, afocal depth of the projected image outstandingly decreases. This causesa problem in that a sufficient exposure energy can not be supplied onlyto some portions corresponding to a part of thickness of the resistlayer.

It is therefore required to selectively use the exposure light sourcehaving a shorter wavelength or the projection optical system having alarger numerical aperture in order to transfer the hyperfiner patterns.As a matter of course, an attempt for optimizing both of the wavelengthand the numerical aperture can be also considered. Proposed in JapanesePatent Publication No. 62-50811 was a so-called phase shift reticle inwhich a phase of the transmitted light from a specific portion among thetransmissive portions of reticle circuit patterns deviates by π from aphase of the transmitted light from other transmissive portions. Whenusing this phase shift reticle, the patterns which are hyperfiner thanin the prior art are transferable.

In the conventional exposure apparatus, however, it is presentlydifficult to provide the illumination light source with a shorterwavelength (e.g., 200 nm or under) than the present one for the reasonthat there exists no appropriate optical material usable for thetransmission optical member.

The numerical aperture of the projection optical system is alreadyapproximate to the theoretical limit at the present time, and a muchlarger numerical aperture can not be probably expected.

Even if the much larger numerical aperture than at present isattainable, a focal depth expressed by ±λ/2NA² is abruptly reduced withan increase of the numerical aperture. There becomes conspicuous theproblem that the focal depth needed for an actual use becomes smallerand smaller. On the other hand, a good number of problems inherent inthe phase shift reticle, wherein the costs increase with morecomplicated manufacturing steps thereof, and the inspecting andmodifying methods are not yet established.

Disclosed, on the other hand, in U.S. Pat. No. 4,947,413 granted to T.E. Jewell et al is the projection lithography method by which a highcontrast pattern projected image is formed with a high resolving poweron the substrate by making the 0th-order diffracted light componentcoming from the mask patterns and only one of the (+) and (−) primarydiffracted light components possible of interference by utilizing aspatial filter processing within the Fourier transform surface in theprojection optical system by use of an off-axis illumination lightsource. Based on this method, however, the illumination light source hasto be off-axis-disposed obliquely to the mask. Besides, the 0th-orderdiffracted light component is merely interfered with only one of the (+)and (−) primary diffracted light components. Therefore, thelight-and-shade contrast of edges of the pattern image is not yetsufficient, the image being obtained by the interference due tounbalance in terms of a light quantity difference between the 0th-orderdiffracted light component and the primary diffracted light component.

SUMMARY OF THE INVENTION

It is a primary object of the present invention, which has been devisedin the light of the foregoing problems, to attain the exposure with ahigh resolving power and large focal depth even when using an ordinaryreticle by making the illumination light incident on a mask at apredetermined angle inclined to the optical axis of an illuminationoptical axis or a projection optical system, providing a member formaking the illumination light incident obliquely on the mask in theillumination optical system and illuminating the mask without any lossin light quantity.

It is another object of the present invention to provide such anarrangement that passage positions of a 0th-order diffracted lightcomponent and (±) primary diffracted light components within a Fouriertransform plane for mask patterns in the projection optical system areset as arbitrary positions symmetric with respect to the optical axis ofthe projection optical system.

To accomplish the objects described above, according to one aspect ofthe present invention, there is provided, in the illumination opticalsystem, a luminous flux distributing member such as a prism, etc. fordistributing the illumination light into at least four luminous fluxespenetrating only a predetermined region on the Fourier transform planefor the mask patterns.

According to another aspect of the present invention, there is provideda movable optical member such as a movable mirror or the like in theillumination optical system to concentrate the luminous fluxes inpredetermined positions on the Fourier transform plane for the maskpatterns. The movable optical member is drivable to cause at least twobeams of illumination light to pass through only the predeterminedregion on the Fourier transform plane with time differences from eachother.

According to still another aspect of the present invention, there areprovided the luminous flux distributing member or the movable opticalmember between an optical integrator such as a fly eye lens, etc. andthe mask or between the light source and the optical integrator.

According to a further aspect of the present invention, the opticalintegrator is divided into a plurality of optical integrator groupswhich are set in discrete positions eccentric from the optical axis. Atthe same time, the illumination light is focused on the plurality ofoptical integrator groups, respectively.

According to still a further aspect of the present invention, theluminous flux distributing member is movable and exchangeable. Theposition in which the luminous flux passes above the Fourier transformplane for the mask patterns is arbitrarily set.

According to yet another aspect of the present invention, in a method ofeffecting the exposure while deviating a substrate position in theoptical-axis direction of the projection optical system from an imageforming surface of the mask patterns, the exposure is performed bymaking the illumination light incident on the mask at an inclined angle.

In accordance with the present invention, it is possible to actualize aprojection type exposure apparatus exhibiting a higher resolving powerand larger focal depth than in the prior art even by employing theordinary reticle. Further, although the effect of improving theresolving power competes with a phase shifter, the conventional photomask can be used as it is. It is also feasible to follow theconventional photo mask inspecting technique as it is. Besides, whenadopting the phase shifter, the effect of increasing the focal depth isobtained, but it is hard to undergo influences of a wavefront aberrationdue to defocus even in the present invention. For this reason, a largefocal depth (focal tolerance) is obtained.

Other objects and advantages of the present invention will becomeapparent during the following discussion taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically illustrating a projection type exposureapparatus in a first embodiment of the present invention;

FIG. 2 is a view depicting a light transmissive substrate (luminous fluxdistributing member) including patterns of periodic structure in thefirst embodiment of the present invention;

FIG. 3 is a view depicting a spatial filter corresponding to thepatterns shown in FIG. 2;

FIGS. 4 and 6 are views each showing a variant form of the periodicstructural patterns in the first embodiment of the present invention;

FIG. 5 is a view illustrating a spatial filter corresponding to thepatterns shown in FIG. 4;

FIG. 7 is a view depicting a spatial filter corresponding to thepatterns shown in FIG. 6;

FIGS. 8, 9, 10, 11 and 12 are views each showing a variant form of theluminous flux distributing member in the first embodiment;

FIG. 13 is a view of a drive unit for the luminous flux distributingmember of FIG. 12;

FIG. 14 is a view schematically showing a light path from the Fouriertransform plane for the reticle to the projection optical system in theprojection type exposure apparatus according to the first embodiment ofthe present invention;

FIGS. 15A and 15C are plan views showing one example of the reticlepatterns formed on the mask;

FIGS. 15B and 15D are views of assistance in explaining the placement ofrespective exit portions (surface illuminant image) on the Fouriertransform surface for the reticle patterns corresponding to FIGS. 15Aand 15C, respectively;

FIG. 16 is a view schematically illustrating a projection type exposureapparatus in a second embodiment of the present invention;

FIGS. 17 and 18 are views showing a variant form of the movable opticalmember according to the present invention;

FIGS. 19A and 19B are flowcharts showing an exposure method in thesecond embodiment of the present invention;

FIG. 20 is a view schematically illustrating a projection type exposureapparatus in a third embodiment of the present invention;

FIGS. 21, 22, 23, 24 and 25 are views each showing a part of an inputoptical system;

FIG. 26 is a view showing an illumination system when incorporating areticle blind into the exposure apparatus of FIG. 20;

FIG. 27 is a view depicting a configuration about a wafer stage of theprojection type exposure apparatus in the third embodiment of thepresent invention;

FIGS. 28A and 28B are graphic charts each showing velocitycharacteristics of a Z-stage and abundance probabilities of the exposurequantity when executing a cumulative focal point exposure method by useof the Z-stage of the wafer stage;

FIG. 29 is a view schematically illustrating a projection type exposureapparatus in a fourth embodiment of the present invention;

FIGS. 30, 31, 32, 33 and 34 are views showing variant forms of the inputoptical system;

FIG. 35 is a plan view taken substantially in the optical-axisdirection, showing a placement of movable fly eye lens groups and aconstruction of a movable member thereof;

FIG. 36 is a view taken substantially in the direction vertical to theoptical axis, showing the construction of FIG. 35;

FIG. 37 is a view schematically illustrating a projection type exposureapparatus in a fifth embodiment of the present invention;

FIG. 38 is a view depicting a concrete construction of the movablemember (switching member of this invention) for exchanging four piecesof holding members consisting of a plurality of fly eye lens groups;

FIG. 39 is a view showing a variant form of the movable member forexchanging the plurality of holding member; and

FIG. 40 is a view schematically showing a fundamental construction of alight path in the first embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will hereinafter be described indetail with reference to the accompanying drawings. FIG. 1 is a blockdiagram illustrating a whole projection type exposure apparatus inaccordance with a first embodiment of the present invention. A luminousflux L1 emitted from an exposure light source 1 such a mercury lamp orthe like and converged by an elliptical mirror 2 is reflected by amirror 3. The luminous flux reflected by the mirror 3 passes through arelay lens 4 and is monochromatized by a wavelength selection element 5.A monochromatized luminous flux L2 is refracted by a mirror 6 and isincident on a fly eye lens 7. At this moment, an incident surface of thefly eye lens 7 is provided in a position substantially conjugate toreticle patterns 28. An exit surface of the fly eye lens 7 is formed ona Fourier transform corresponding plane (Fourier transform plane) of thereticle patterns 28 or in the vicinity of this plane. An aperture stop 8is provided in close proximity to the exit surface of the fly eye lens7. A numerical aperture of illumination light L3 is determined by adrive unit 9 for making variable a size of an opening of the aperturestop 8. The illumination light L3 is reflected by a mirror 10.Illuminated with the illumination light through a condenser lens 11 is adiffraction grating pattern plate (light transmissive flat plate) 12incised with diffraction grating patterns 13 a. This diffraction gratingpattern plate 12 functions as a luminous flux distribution member in thepresent invention. This plate 12 is attachable/detachable andinterchangeable. At this time, the diffraction grating pattern plate 12is provided on a surface substantially conjugate to the hyperfinereticle pattern surfaces 28 formed on a reticle 27. The reticle patterns28 may be herein isolated patterns or patterns having a periodicstructure.

As described above, an optical integrator such as the fly eye lens andfibers is used in an illumination optical system for illuminating thereticle with the light. Made uniform is an intensity distribution of theillumination light with which the reticle is illuminated. In the case ofemploying the fly eye lens to optically effect this homogenizingprocess, a reticle side focal surface and a reticle surface are linkedbased substantially on a relation of Fourier transform. The reticle sidefocal surface and a light source side focal surface are also linkedbased on the relation of Fourier transform. Hence, the pattern surfaceof the reticle and the light source side focal surface (precisely thelight source side focal surface of each individual lens element of thefly eye lens) are linked based on an image forming relation (conjugaterelation). For this reason, on the reticle, the illumination beams fromthe respective elements (secondary illuminant image) of the fly eye lensare added (overlapped) and thereby averaged. An illuminance homogeneityon the reticle can be thus enhanced.

FIG. 2 is a plan view showing one example of the diffraction gratingpattern plate.

The diffraction grating pattern plate 12 is a transparent substrate offused quartz or the like and is formed with the diffraction gratingpattern 13 a. The Diffraction grating patterns 13 a are conceived asline-and-space patterns formed of a metal thin film of Cr and the like.Note that at this time, a pitch Pg of the diffraction grating patterns13 a is desirably substantially given by Pg=2Pr×M (m is themagnification of image formation between the diffraction grating pattern13 a and the reticle patterns 28) with respect to a pitch Pr of thereticle patterns 28. A duty ratio thereof is not necessarily 1:1 but maybe arbitrary.

Now, returning to the description of FIG. 1, (−) primary diffractedlight L4 and (+) primary diffracted light L5 generated by thediffraction grating pattern plate 12 are separated from each other by acondenser lens 15 on a Fourier transform plane 50 in the illuminationoptical system. The beams of light are then condensed in a positioneccentric from the optical axis of the illumination optical system (or aprojection optical system (29)). The positions through which the beamsof (±) primary diffracted light L4, L5 pass above the Fourier transformplane are symmetric with respect to an optical axis AX. A spatial filter16 is provided on the Fourier transform plane or on a plane in thevicinity of the Fourier transform plane. Light transmissive positions(openings) are provided in such positions as to transmit only the beamsof diffracted light ((±) primary diffracted light L4, L5 in thisembodiment) of the specific order among the beams of diffracted lightgenerated from the diffraction grating patterns 13 a. Note that thisspatial filter 16 may be such a variable type filter as to make variablea position and a configuration of the transmissive portion or may be afilter of such a type that the spatial filter 16 itself isattachable/detachable and interchangeable. The spatial filter 16 ispreferably provided with, when the 0th-order diffracted light isgenerated from the diffraction grating pattern 13 a, a Cr thin filmhaving a size enough to shield the 0th-order diffracted light. Beams oflight of unnecessary orders can be also shielded.

FIG. 3 depicts a spatial filter 16 a suitable when using the diffractiongrating patterns 13 a shown in FIG. 2. An oblique line portion indicatesa light shielding portion. A radius of the spatial filter 16 a is setgreater than a total numerical aperture of the illumination opticalsystem. Two light transmissive portions (openings) 16 a 1, 16 a 2 areprovided in portions symmetric with respect to the central point of thespatial filter 16 a.

An intensity distribution (positions of luminous fluxes) on the Fouriertransform plane of the illumination optical system required differsdepending on the directivity of the reticle pattern 28. It is, however,desirable that the directivity of the diffraction grating patterns 13 abe equal to the directivity of the reticle patterns 28. In this case, itis not necessary that the directivities be identical. The directivity ofthe diffraction grating patterns 13 a projected on the reticle pattern28 may be coincident with a large proportion of the directivity of thereticle patterns 28. To implement these requirements, intrinsicdiffraction grating patterns determined for the respective reticlepatterns 28 are incised in individual diffraction grating patternplates. Simultaneously when replacing a reticle 27, the reticle 27 maybe replaced while matching it with the diffraction grating patternplate.

The diffraction grating patterns 13 a are determined by the pitch orline width and the directivity of the reticle patterns 28. Hence, thesame diffraction grating patterns plate may be used in common to aplurality of reticles having patterns in which the pitches, line widthsand the directivities are substantially equal.

If the directivities of the plurality of reticles are different, theymay be made coincident with the directivities of the patterns on therespective reticles by rotating the diffraction grating pattern plate 12within a plate vertical to the optical axis. Further, if the diffractiongrating pattern plate 12 is rotatable (through, e.g., 90°), acorrespondence can be given to such a case that the line-and-spacepattern directions of the reticle patterns 13 a are different fromdirections x, y. The relay lens 15 is set as a zoom lens (afocal zoomexpander and the like) composed of a plurality of lens elements, whereina condensing distance is variable by changing a focal distance. In thiscase, however, the conjugate relation between the diffraction gratingpattern plate 12 and the reticle 27 should be kept. Further, an image ofthe pattern 13 a may be rotated by use of an image rotator.

For instance, the diffraction grating patterns 13 a may be employed in astate of being rotated about the optical axis of the illuminationoptical system to obtain an arbitrary angle in accordance with thedirectivity of the reticle patterns 28.

Now, as illustrated in FIG. 1, the luminous fluxes L4, L5 passingthrough the spatial filter 16 are led to a reticle blind 20 via acondenser lens 19. The reticle blind 20 is provided on a surfacesubstantially conjugate to the reticle pattern surfaces 28 and is afield stop for illuminating only the specific area on the reticle 27with the light. This reticle blind 20 has an aperture openable andclosable, with the aid of a drive system 21 and is capable of adjustinga size of the illumination area on the reticle 27. The reticle 27 isilluminated with luminous fluxes L6, L7 passing through the reticleblind 20 through condenser lenses 22, 26 and a mirror 24 disposedsubstantially in the vicinity of the Fourier transform plane. Theluminous fluxes L6, L7 are incident on the reticle patterns 28. Thebeams of diffracted light generated from the reticle patterns 28 arecondensed to form an image on a wafer 30 by means of a projectionoptical system 29. The wafer 30 is two-dimensionally movable within theplane vertical to the optical axis. The wafer 30 is placed on a waferstage 31 movable in the optical-axis direction.

FIG. 40 schematically illustrates a fundamental configuration of lightpaths for illumination beams in an exposure apparatus in thisembodiment. Referring to FIG. 40, the light transmissive portions(openings) of the spatial filter 16 are disposed in position eccentricfrom the optical axis AX of the projection optical system or theillumination optical system on the Fourier transform plane. A coordinateposition of the luminous fluxes passing through the Fourier transformplane is eccentric from the optical axis AX.

Now, the illumination light L5 emitted from the of the spatial filter 16is incident on the reticle 27 via the condenser lens 26. The reticlepatterns 28 depicted on the reticle (mask) 27 typically contain a largenumber of periodic patterns. Therefore, a 0th-order diffracted lightcomponent D0, (±) primary diffracted light components Dp, Dm or otherhigher-order diffracted light components are generated in directionscorresponding to degrees of fineness of the patterns from the reticlepatterns 28 illuminated with the light. At this moment, the illuminationluminous fluxes (central line) are incident on the reticle 27 at aninclined angle. Hence, the diffracted light component of the respectiveorders are also generated from the reticle patterns 28 with aninclination (angular deviation) as compared with the verticalillumination. The illumination light L6 shown in FIG. 40 is incident onthe reticle 27 with an inclination ψ to the optical axis.

The illumination light L6 is diffracted by the reticle patterns 28,thereby generating a 0th-order diffracted light component Do travelingin a direction with the inclination ψ to the optical axis AX, a (+)primary diffracted light component Dp with an inclination θp to the0th-order diffracted light component and a (−) primary diffracted lightcomponent Dm traveling with an inclination θm to the 0th-orderdiffracted light component Do. The illumination light L6 is, however,incident on the reticle patterns at the inclined angle ψ to the opticalaxis AX of the projection optical system 29 both sides of which aretelecentric. For this reason, the 0th-order diffracted light componentDo also travels in the direction inclined at the angle ψ to the opticalaxis AX of the projection optical system.

Hence, the (+) primary diffracted light component Dp travels in adirection of (θp+ψ) to the optical axis AX, while the (−) primarydiffracted light component Dm goes in a direction of (θm−ψ) to theoptical axis AX.

At this time, the diffracted angles Op, Om are expressed such as:

sin (θp+ψ)−sin ψ=λ/P  (1)

sin (θm−ψ)+sin ψ=λ/P  (2)

where it is assumed that both of the (+) primary diffracted lightcomponent Dp and (−) primary diffracted light component Dm penetrate apupil plane (the Fourier transform surface of the reticle patterns) 51of the projection optical system 29.

When the diffracted angle increases with finer reticle patterns 28, the(+) primary diffracted light component Dp traveling in the directioninclined at the angle of (θp+ψ) at first becomes incapable ofpenetrating the pupil surface 51 of the projection optical system 29.Namely, there is developed a relation such as sin (θp+ψ)>NA_(R). A beamof illumination light L6 is incident with an inclination to the opticalaxis AX, and hence the (−) primary diffracted light component Dm iscapable of incidence on the projection optical system 29 even at thediffracted angle of this time. Namely, there is developed a relationsuch as sin (θm−ψ)<NA_(R).

Produced consequently on the wafer 30 are interference fringes by twoluminous fluxes of the 0th-order diffracted light component Do and the(−) primary diffracted light component Dm. The interference fringes areconceived as an image of the reticle patterns 28. A contrast ofapproximately 90% is obtained when the reticle patterns 28 have aline-and-space of 1:1, and patterning of the image of the reticlepatterns 28 can be effected on a resist applied over the wafer 30.

A resolving limit at this moment is given by:

sin (θm−ψ)=NA _(R)  (3)

Hence, a reticle-side pitch of the transferable minimum pattern is givenby:

NA _(R)+sin ψ=λ/P P=λ/(NA _(R)+sin ψ)  (4)

Now, supposing that sin ψ is set to approximately 0.5×NA_(R) as oneexample, the minimum pitch of the pattern on the transferable reticle isgiven by:

P=λ/(NA _(R)+0.5NA _(R))=2λ/3NA _(R)  (5)

On the other hand, in the case of a known projection exposure apparatusin which a distribution of illumination light on the pupil plane 51 ofthe Fourier transform plane falls within a circular range (rectangularrange) about the optical axis AX, the resolving limit is expressed bysin θm=λ/P≅NA_(R). The minimum pitch is given by P≅λ/NA_(R). It can betherefore understood that the projection type exposure apparatus in thisembodiment attains a higher resolving power than in the known exposureapparatus.

The following is an elucidation about why a focal depth becomes large onthe basis of a method of forming image forming patterns on the wafer byuse of the 0th-order diffracted light component and the primarydiffracted light component while the reticle patterns are irradiatedwith the exposure light in a specific incident direction at a specificincident angle.

As illustrated in FIG. 40, when the wafer 30 is coincident with thefocal position (the best image forming surface) of the projectionoptical system 29, all the individual diffracted light componentsemerging from one point of the reticle patterns 28 and reaching onepoint on the wafer 30, even if they pass through any part of theprojection optical system 29, have an equal length of light path. Forthis reason, even when the 0th-order diffracted light componentpenetrates substantially the center (in the vicinity of the opticalaxis) of the pupil surface 51 of the projection optical system 29, the0th-order diffracted light component and other diffracted lightcomponents are equal in terms of lengths of their light paths, and amutual wavefront aberration is zero. When the wafer 30 is in a defocusstate (the wafer 30 does not coincide with the focal position of theprojection optical system 29), however, the lengths of the high-orderdiffracted light components obliquely falling thereon are short in frontof the focal point as compared with the 0th-order diffracted lightcomponent passing in the vicinity of the optical axis. Whereas in rearof the focal point (closer to the projection optical system 29), thelengths increase. A difference therebetween corresponds to a differencebetween the incident angles. Hence, the 0th-order, primary, . . .diffracted light components mutually form the wavefront aberration,resulting in creation of unsharpness in front and in rear of theposition of the focal point.

The wavefront aberration caused by the defocus described above isdefined as a quantity given by ΔFr²/2, where ΔF is the amount ofdeviation from the focal point position of the wafer 30, and r (r=sinθw) is the sine of an incident angle θw in the case of (−) incidence ofthe individual diffracted light component. (At this time, r represents adistance from the optical axis AX on the pupil plane 51.) In theconventional known projection type exposure apparatus, the 0th-orderdiffracted light component Do passes in the vicinity of the optical axisAX, and hence r (0th-order)=0. On the other hand, in the (±) primarydiffracted light components Dp, Dm, r (primary)=M·λ/P (M is themagnification of the projection optical system).

Therefore, the wavefront aberration due to defocusing of the 0th-orderdiffracted light component Do and the (+) primary diffracted lightcomponents Dp, Dm is given by:

ΔF·M ²(λ/P)²/2.

On the other hand, in the projection type exposure apparatus accordingto this invention, as illustrated in FIG. 40, the 0th-order diffractedlight component Do is generated in the direction inclined at the angle ψto the optical axis AX. Thus, the distance of the 0th-order diffractedlight component from the optical axis AX on the pupil plane 51 isexpressed such as r (0th-order)=M·sin ψ.

Further, the distance of the (−) primary diffracted light component Dmfrom the optical axis on the pupil surface is expressed such as r ((−)primary)=M·sin ψ(θm−ψ). At this time, if sin ψ=sin (θm−ψ), a relativewavefront aberration due to defocusing of the 0th-order diffracted lightcomponent Do and the (−) primary diffracted light component Dm becomeszero. Even when the wafer 30 deviates slightly in the optical-axisdirection from the position of the focal point, it follows that theunsharp image of the patterns 28 does not become larger than in theprior art. Namely, the focal depth increases. As shown in the formula(2), sin (θm−ψ)+sin ψ=λ/P, and hence it is possible to remarkablyincrease the focal depth on condition that the incident angle φ of theillumination luminous flux L6 to the reticle 27 is made to have arelation such as sin φ=λ/2P with respect to the patterns having thepitch P.

Herein, as discussed above, each of the luminous fluxes L6, L7 isincident on the reticle 28 at the inclined angle ψ in symmetry withrespect to the optical axis of the projection optical system or theillumination optical system. Generated from the patterns 28 are the0th-order diffracted light component Do, a (−) primary light componentDm and a (+) primary light component Dp.

The incident angle ψ is prescribed by a numerical aperture NA of theprojection optical system as well as by the reticle patterns 28. Asexpressed in the formula (4), this incident angle is selectively set toan incident angle corresponding to the minimum value of the reticlepattern pitch. The incident direction is desirably set to a pitch arraydirection of the reticle patterns. The optimum conditions of theincident angle will be explained later.

Herein, as described above, the diffraction grating pattern plate 12 isdisposed in the position substantially conjugate to the reticle patterns28. The diffraction grating patterns 13 a are therefore projected on thereticle patterns 28 via the illumination optical system. For thisreason, a light-and-shade image assuming the diffraction gratingconfiguration is formed on the reticle patterns 28, and the uniformityin amount of illumination light is thereby deteriorated. However, thediffraction grating pattern plate 12 incised with the diffractiongrating patterns 13 a is oscillated or shifted by one pitch of thediffraction grating patterns 13 a or by approximately an integermultiple or greater during an exposure period (while an unillustratedshutter is opened) per shot by a drive member 14 such as a motor, apiezoelement and the like. The light-and-shade image is thereby shiftedby approximately one pitch or larger during the exposure period pershot. The luminance is averaged (homogenized) in terms of time, therebykeeping well the uniformity in quantity of the illumination light. Thedirection in which the light-and-shade image is shifted or oscillated ispreferably set to exhibit a less correlation with the direction of thediffraction grating patterns 13 a. For instance, the image is allowed tomake a circular motion (synthesized with the oscillations in thedirections x and y) wherein a diameter is set to a value which exceedsthe pitch Pg of the patterns 13 a within the plane vertical to theoptical axis.

At this time, one or more optical members closer to the reticle 27 thanthe diffraction grating pattern plate 12 may be shifted, oscillated orallowed to make the circular motion under the same conditions within theillumination optical system in place of the diffraction grating patternplate 12. FIG. 1 shows an example where drive members 23, 25 areattached to the condenser lens 22 and the mirror 24.

The light-and-shade image is averaged within the exposure period bygiving the above-described shifting, oscillating or circular motion. Theillumination light quantity on the reticle patterns 28 can be keptuniform.

There is, however, a possibility to cause unevenness in the lightquantity on the reticle pattern surfaces 28 due to a dispersion indiffraction efficiency or in transmissivity within the pattern planewhich is derived from a manufacturing error of the diffraction gratingpatterns 13 a. To prevent this phenomenon, a light scattering member 17such as a diffusion plate of a lemon skin and the like may be disposedin close proximity to the Fourier transform plane 50.

The light emerging from one point on the diffraction grating patterns 13a is scattered by the light scattering member 17 and serves forillumination over a wide area of the reticle pattern surfaces 28. Inother words, the light from the wide area of the diffraction gratingpatterns 13 a reaches one point on the reticle pattern surfaces 28. Alocal error in manufacture of the diffraction grating patterns 13 a isrelieved. At this time, the light scattering member 17 is shifted,oscillated or rotated by a motor 18 during the exposure period per shot,whereby a time averaging effect is produced. This makes it easier toeliminate the dispersion in the quantity of the illumination light.

Note that when shifting, oscillating or rotating the light scatteringmember 17, the optical members such as the diffraction grating patternplate 12 or the condenser lens 22 and the mirror 24 may not be shifted,oscillated or rotated.

This light scattering member 17 provided in the vicinity of the Fouriertransform plane deteriorates the image of the diffraction gratingpatterns 13 a but does not cause extreme fluctuations in the angularrange of the incident angles of the illumination light incident on thereticle pattern surface 28.

In addition, the fiber bundles may be laid leastwise larger than thespot beams on the Fourier transform plane or over the entire Fouriertransform plane in place of the light scattering member 17 todeteriorate the light fluxes. Further, the effect to deteriorate theimage can be enhanced by a combination with the light scattering member17.

Incidentally, the device depicted in FIG. 1 includes: a main controlsystem 58 for generalizing/controlling the device; a bar code reader 61for reading bar codes BC representing the names prepared on a side ofthe reticle patterns 28 in the course of carrying the reticle 27 justabove the projection optical system 29; and a keyboard 63 for inputtingcommands and data from the operator. Registered beforehand in the maincontrol system 58 are the names of a plurality of reticles dealt with bythis stepper and stepper operation parameters corresponding to therespective names. The main controller system 58 outputs, when the barcode reader 61 reads the reticle bar code BC, the previously registeredinformation on the shift and the rotation of the diffraction gratingpattern plate 12 to the drive member 14 as one of the operationparameters which corresponds to that name. The optimum distribution ofthe light quantity can be thereby formed on the Fourier transformsurface 50 in accordance with the reticle patterns on the reticle. Asone of the parameters corresponding to the names of the reticles, theinformation on the replacement of the diffraction grating pattern plate12 is inputted to a diffraction grating replacing member 62. Thediffraction grating pattern plate 12 optimal to the reticle patterns 28formed on the reticle is thereby selectable. The operations discussedabove are executable by the operator's inputting the commands and datadirectly to the main control system 58 from the keyboard 63.

Now, in order to intensify the effect of improving the resolving powerin this embodiment, preferably σ=0.1 to 0.3 by adjusting the numericalaperture 8 of the illumination system. The reason for this is that theimprovements of the resolving power and of the focal depth are notattainable if the value σ is too large, and whereas if too small, afidelity declines. Hence, when an exit area of the fly eye lens 7 of theabove-described illumination optical system is set to 1, it is desirableto manufacture a fly eye lens having an exit area of, e.g. 0.3 incontrast with that value. The illumination optical system from theelliptical mirror 2 to the fly eye lens 7 may preferably be constructedto maximize the light quantity with respect to σ≅0.3. In addition, thevalue σ may be variable by changing the width of luminous fluxesincident on the fly eye lens 7 with the lens system 4 being composed ofa zoom lens (afocal zoom lens).

The foregoing positions of the respective mirrors are not limited to theabove-mentioned. For instance, the mirror 24 fitted with the drivemember 25 may be disposed closer to the spatial filter 16 than thereticle blind 20.

Next, there will be explained a case where the reticle patterns 28 arenot oriented uniformly over the entire surface of the reticle butoriented partially in different directions.

For example, a case where the reticle patterns 28 have the periodicstructure in two directions x, y will be described. Where the reticlepatterns 28 have the periodic structure in the two directions x, y,there may be employed the diffraction grating pattern plate 12 formedwith diffraction grating patterns 13 b arrayed partially in differentdirections as shown in FIG. 4. Referring to FIG. 4, diffraction gratingpatterns 13 b 1, 13 b 3 correspond to the reticle patterns 28 having theperiodic structure in the direction y. Diffraction grating patterns 13 b2, 13 b 3 correspond to the reticle patterns 28 having the periodicstructure in the direction x. At this time, the pitch array direction ofthe diffraction grating patterns 13 b 1, 13 b 3 is equalized to thepitch array direction of the reticle patterns 28 having the periodicstructure in the direction y. The pitch array direction of thediffraction grating patterns 13 b 2, 13 b 3 is equalized to the pitcharray direction of the reticle patterns 28 having the periodic structurein the direction y.

FIG. 5 is a diagram illustrating a spatial filter 16 b corresponding tothe diffraction grating pattern 13 b depicted in FIG. 4. The spatialfilter 16 b includes light transmissive portions (openings) 160 a, 160b, 160 c, 160 d. The oblique line portion indicates a light shieldingportion. The light transmissive portions 160 a, 160 c transmit thediffracted light generated from the diffraction grating patterns 13 b 1,13 b 3. A spacing between the light transmissive portions 160 a, 160 bis determined by a pitch of the diffraction grating patterns 13 b 1, 13b 3. A direction and an angle of the diffracted light incident on thereticle patterns are determined by positions of the beams of refractedlight at the spatial filter 16, i.e., by positions of the lighttransmissive portions 160 a, 160 c.

Similarly, the light transmissive portions 160 b, 160 d transmit thediffracted light from the diffraction grating patterns 13 b 2, 13 b 4. Adirection and an angle of the luminous flux incident on the reticlepatterns 28 are determined by the position of the refracted light on thespatial filter 16 which is conditional to the pitch of the diffractiongrating patterns 13 b 2, 13 b 4.

A configuration of the diffraction grating pattern 13 b is not limitedto the line-and-space depicted in FIG. 4 but may be a checked gratingpattern 13 c illustrated in FIG. 6. The pitch array direction isdesirably matched with the array direction of the reticle patterns 28.As discussed above, if the periodic patterns on the reticle are arrayedin the two directions x, y, as illustrated in FIG. 6, the pitches of thechecked grating pattern 13 c may be set in the directions x, y. A dutyratio thereof is not limited to 1:1.

FIG. 7 illustrates a spatial filter 16 c for the checked grating pattern13 c shown in FIG. 6. The spatial filter 16 c includes lighttransmissive portions 161 a, 161 b, 161 c, 161 d. The oblique lineportion indicates the light shielded portion.

Spacings between the light transmissive portions 161 a, 161 b and 161 d,161 c are determined by the x-directional pitch of the diffractiongrating pattern 13 c shown in FIG. 6. Spacings between the lighttransmissive portions 161 a, 161 d and 161 b, 161 c are determined bythe y-directional pitch of the diffraction grating pattern 13 c shown inFIG. 6. Where the reticle patterns 28 have the periodic structure in thetwo directions x, y, the illumination light penetrating the lighttransmissive portions 161 a, 161 d is incident on the reticle patterns28 having the x-directional periodic structure, thereby generating the(+) primary diffracted light component. This diffracted light componentpasses through substantially the same position as that of the 0th-orderdiffracted light component of the illumination light which haspenetrated the light transmissive portions 161 b, 161 c respectively onthe pupil surface 51 of the projection optical system 29. Reversely, theillumination light penetrating the light transmissive portions 161 b,161 c is incident on the reticle patterns 28 having the x-directionalperiodic structure, thereby generating the (−) primary diffracted lightcomponent. This diffracted light component passes through substantiallythe same position as that of the illumination light which has penetratedthe light transmissive portions 161 a, 161 d respectively on the pupilsurface 51 of the projection optical system. Distances from the opticalaxis to the respective light transmissive portions 161 a, 161 b, 161 c,161 d are equally set. Therefore, the 0th-order diffracted lightcomponent and the (+) primary diffracted light component or the (−)primary diffracted light component pass through the positions havingsubstantially equal distances from the optical axis on the pupil surfaceof the projection optical system. Four beams of illumination lightpassing through the light transmissive portions 161 a to 161 d areincident on the reticle patterns 28, thereby generating (+) or (−)primary diffracted light component. Combined light components of any oneof these primary diffracted light components and the 0th-orderdiffracted light component all reach the wafer 30, whereby an imagehaving, as described above, a contrast of approximately 90%, is formed.Further, the 0th-order diffracted light component and the primarydiffracted light components travel through the positions havingsubstantially equal distances from the optical axis AX on the pupilsurface 51 of the projection optical system 29, and hence the focaldepth is also great.

The case of the patterns having the periodicity in the direction x hasbeen described so far. The patterns having the periodicity in thedirection y are, however, available. The directions of the gratings arenot limited to the above-mentioned but may include, e.g., a slantdirection in accordance with the reticle patterns. Two pieces of lighttransmissive substrates formed with the repetitive diffraction gratingpatterns 13 a shown in FIG. 2 are disposed so that the pattern surfacesconfront each other. Two flat plates are relatively rotated about theoptical axis of the illumination optical system, and arbitrary patternsmay be formed by a adjusting the relative positions of the respectivepatterns. Further, the repetitive patterns assuming other arbitraryconfigurations may also be available. The diffraction grating patterns13 may be not only the rectilinear patterns but also patterns having theperiodic structure, e.g., homocentric grating patterns (Fresnel zoneplate, etc.) and homocentric elliptical patterns. Additionally, thepatterns having arbitrary light-and-shade portions in the two directionx, y may also be created by use of liquid crystal and the like. In thesecases also, the spatial filter 16 having the transmissive portionsdetermined based on the positions of diffracted light may be used.

The diffraction grating pattern plate 12 may be the one in which a lightshielding film of Cr and the like undergoes patterning on the surface ofa transmissive substrate, e.g., a glass substrate. Alternatively, theplate 12 may be the one provided with so-called phase gratings in whicha dielectric film of SiO₂ or the like is subjected to patterning. Thephase gratings exhibit such advantages that the Oth-order diffractedlight component can be restrained, the spatial filter 16 can be alsoomitted, and a loss of the light quantity is small.

As discussed above, the incident directions and the incident angles ofthe (plurality of) illumination luminous fluxes incident on the reticlepatterns 28 are prescribed corresponding to the reticle patterns 28. Theincident directions and angles can be adjusted arbitrarily by changingthe directivity and the pitch of the diffraction grating patterns 13 a.For example, as explained earlier, the diffraction grating pattern plate12 is replaced with the one having the different pitches, thereby makingvariable the positions of the luminous fluxes incident on the Fouriertransform plane. It is therefore possible to attain an arbitrarydistribution of the illumination light quantity on the Fourier transformplane without causing a considerable loss of the illumination lightquantity. As stated before, the transmitting positions of the luminousfluxes on the Fourier transform plane are made variable, whereby theincident angle of the illumination light to the reticle patterns 28 isalso made variable (the angle of the luminous fluxes incident on theprojection optical system is adjustable to a desired angle). For thisreason, it is feasible to obtain the projection exposure apparatushaving a high resolving power and a smaller loss of the light quantity.The luminous flux transform member is intended to generate the lightquantity distribution assuming an arbitrary configuration in accordancewith the incident angle to the reticle patterns 28 on the Fouriertransform plane or in the vicinity of this Fourier transform plane.Eliminated is an adjustment of the relative positional relation with thereticle patterns.

Note that there will be mentioned in detail the determination about thepositions (on which the light quantity distributions concentrate on theentire Fourier transform plane) of the luminous fluxes incident on theFourier transform plane 50.

The following is an explanation of a method of deteriorating the imageby providing optical elements in the light transmissive portions of thespatial filter 16 by way of an example of variant form of the means fordeteriorating the image.

Transmissive flat plates having different thicknesses and refractiveindices are adhered to the respective light transmissive portions of thespatial filter 16. The beams of light penetrating the individual lighttransmissive portions travel along the light paths which are each longerby a value of (diffraction grating pattern plate thickness×refractiveindex). If a difference between the lengths of the light paths of theluminous fluxes penetrating the respective transmissive portions islarger than a coherent length of the illumination light, the beams oflight penetrating the respective transmissive portions do not interferewith each other on the reticle pattern surfaces. Namely, it implies thatno image of the diffraction grating patterns is formed. For instance, ifthe illumination light is an i-beam (wavelength=0.365 μm, wavelengthwidth=0.005 μm) of the mercury lamp, the coherent length of theillumination light is approximately 27 μm. Where the glass having arefractive index of 1.5 is used as the above-described diffractiongrating pattern plate, a difference (Δt) between the thicknesses of theflat plates adhered to the respective openings is expressed such as:

Δt×(1.5−1)≧27 μm

where the refractive index of the air is 1. The difference defined byΔt≧54 μm may suffice.

Hence, if the glasses individually having a refractive index of, e.g.,1.5 and thicknesses of 1000 μm, 1060 μm (thickness-difference is 60^(μ)m) are adhered to the respective openings of the spatial filterillustrated in, e.g., FIG. 3, the interference fringes on the reticlepattern surfaces—i.e., the image of the diffraction gratingpatterns—disappear (deterioration).

Where the light transmissive flat plates having the differentthicknesses and refractive indices are adhered to the openings of thespatial filter 16. in this manner, the diffraction grating patterns 13and the optical member or the light scattering member 17 may not beoscillated, shifted or rotated.

If a coherence length of the illumination light is large, and whenusing, e.g., a laser beam source, preferably an optical rotatory elementsuch as crystal may be adhered to one opening of the spatial filter 16to rotate a polarizing direction of the transmission light throughapproximately 90°. Adhered to other openings are the transmissive flatplates of glass and the like having substantially equal length of thelight path as that of the optical rotary element. Where the spatialfilter described above is employed, almost a half of the luminous fluxeswith which the reticle pattern surfaces are irradiated are orthogonal(alternatively, circularly polarized light in the reverse direction) toeach other in terms of their polarizing directions. Therefore, theinterference fringes—viz., the image of the diffraction gratingpatterns—are deteriorated. The diffraction grating patterns 13 arepositioned with slight deviations in the optical-axis direction from theconjugate position to the reticle patterns 28, with the result that theimage of the diffraction grating patterns 13 projected on the reticlepatterns 28 may be deteriorated (defocused).

Deteriorated (homogenized) by the image deteriorating means on the basisof the above-described construction are the unnecessary light-and-shadefringes (the image of the diffraction grating patterns) which areproduced by projecting (image-forming) the diffraction grating patternsserving as the luminous flux distributing member on the reticle patternsurfaces through the illumination optical system. Alternatively, thefringes are averaged in time and then homogenized in terms of thedistribution of the image surface light quantity. An unevenness ofilluminance on the reticle pattern surfaces can be prevented. Further,it is feasible to remarkably reduce the manufacturing costs for theluminous flux transform members without being influenced by the defectsin manufacturing the luminous flux distributing members.

The diffraction grating pattern plate 12 may be not only thetransmissive pattern plate but also a reflective pattern plate shown inFIG. 8. The optical member for transforming the illumination lightdescribed above into a plurality of luminous fluxes and forming anarbitrary light quantity distribution on the Fourier transform plane 50is not limited to the diffraction grating pattern plate 12 or 12A.

FIG. 9 is a schematic diagram showing an arrangement in which a prism 33formed with a plurality of refractive surfaces is employed as a member(luminous flux distributing member) for guiding a plurality of luminousfluxes onto the Fourier transform plane 50 and forming an arbitrarylight quantity distribution on the Fourier transform plane. Theconfigurations toward the light source from a relay lens 11 and towardthe reticle from a relay lens 15 are the same as those shown in FIG. 1.The prism 33 in FIG. 9 is divided into two refractive surfaces with theoptical axis AX serving as a boundary. The illumination light incidentupwardly of the optical axis AX is refracted upwards, whereas theillumination light incident downwardly of the optical axis AX isrefracted downwards. Hence, the illumination luminous fluxes can beincident on the Fourier transform plane in accordance with a refractingangle of the prism 33. The dividing number of the refractive surfaces isnot limited to 2 but may be any number in accordance with a desiredlight quantity distribution on the Fourier transform plane. The dividingpositions are not necessarily symmetric positions with respect to theoptical axis AX.

The incident positions of the illumination luminous fluxes incident onthe Fourier transform plane 50 are made variable by exchanging the prism33.

Further, the prism 33 at this time may be a polarization beam splittersuch as wollaston prism, etc. In this case, however, the polarizingdirections of the split luminous fluxes are different, and hence thepolarization properties may be arranged in one direction, consideringthe polarization property of the resist of the wafer 30. The device, asa matter of course, incorporates a function to exchange the prism andthe like.

FIG. 10 shows an example where a plurality of mirrors 34 a, 34 b, 34 c,34 d are employed as luminous flux distributing members. Theillumination light passing through the relay lens system 11 is soreflected as to be separated into two directions through the primarymirrors 34 b, 34 c and guided by the secondary mirrors 34 a, 34 d. Theillumination light is again reflected and reaches the Fourier transformplane. Each of the mirrors 34 a, 34 b, 34 c, 34 d is provided with aposition adjusting mechanism and a mechanism for adjusting an angle ofrotation about the optical axis AX. Based on these mechanisms, theillumination light quantity on the Fourier transform surface 50 isarbitrarily made variable. Further, the mirrors 34 a, 34 b, 34 c, 34 dmay be plane, convex or concave mirrors. As depicted in FIG. 10, it ispermitted that some luminous fluxes are not reflected once by themirrors but are incident directly on the Fourier transform plane 50 fromthe relay lens 4. Besides, lenses may be interposed between thesecondary mirrors 34 a, 34 d and the Fourier transform plane.

Prepared by twos in FIG. 10 are the primary mirrors 34 b, 34 c and thesecondary mirrors 34 a, 34 d. The numerical quantity is not limited tothis value. The mirrors may be disposed appropriately corresponding tothe desired illumination light incident on the Fourier transform planein accordance with the reticle patterns 28. All the mirrors are, as thenecessity arises, constructed to retreat up to such positions that theillumination luminous fluxes strike on the mirrors.

FIG. 11 illustrates an example where a beam splitter is employed as aluminous flux distributing member. The configurations toward the lightsource from the relay lens 11 and towards the reticle from the spatialfilter 16 are the same as those shown in FIG. 1. As illustrated in FIG.11, the illumination light traveling through the relay lens 11 is splitinto two luminous fluxes LA1, LA2 by means of a beam splitter 38provided in the illumination optical system. The luminous fluxes LA1,LA2 are distributed as those having a certain magnitude (thickness) onthe Fourier transform plane 50 through lens systems 39, 40 and planeparallels 41, 42. The lens systems 39, 40 are properly selected, wherebya magnitude of the illumination light quantity distribution on theFourier transform plane 50 can be arbitrarily set. The plane parallels41, 42 are minutely movable (inclinable) by drive systems 43, 44. Thedistributed positions of the luminous fluxes distributed on the Fouriertransform plane 50 can be minutely adjustable. The drive systems 43, 44are constructed of motors, gears or piezoelements and so on.

The luminous flux distributing member may involve the use of a waveguidemember such as optical fibers and the like. FIG. 12 is a schematicdiagram in a case where an optical fiber bundle 35 is used as a luminousflux distributing member. The configurations towards the light sourcefrom the relay lens 11A and towards the reticle from the spatial filter16 are the same as those shown in FIG. 1. The illumination lightemerging from the light source and penetrating the relay lens 11A isincident via an incident portion 351 on the optical fiber bundle 35while being adjusted to a predetermined numerical aperture (NA). Theillumination luminous fluxes incident via the incident portion 351 onthe optical fiber bundle 35 are split into a plurality of luminousfluxes and exit a plurality of exit portions 35 a, 35 b. The pluralityof exit portions 35 a, 35 b are provided in positions eccentric from theoptical axis AX on the Fourier transform plane (pupil plane of theillumination optical system) 50. Only the luminous fluxes which exitonly the exit portions 35 a, 35 b are formed in close proximity to theFourier transform plane.

It is therefore possible to form an arbitrary distribution of theillumination light quantity in the vicinity of the Fourier transformplane even by using the optical fiber bundle 35 as in the same way withthe above-mentioned diffraction grating pattern plate 12.

At this time, lenses (e.g., field lenses) may be interposed between theexit portions 35 a, 35 b of the optical fiber bundle 35 and the spatialfilter 16.

As discussed above, the incident angles of the illumination lightfalling on the reticle 27 and the reticle patterns 28 are determined bythe positions (eccentric from the optical axis AX) of the exit portions35 a, 35 b within the plane vertical to the optical axis AX. For thisreason, the exit portions 35 a, 35 b are independently movable with theaid of movable members 36 a, 36 b for adjusting the positions of theexit portions 35 a, 35 b within the Fourier transform surface.

Next, an embodiment of the movable portions movable on the fiber exitportions will be explained with reference to FIGS. 12 and 13. FIG. 12 isa sectional view, as in FIG. 1, taken substantially in the directionvertical to the optical axis. FIG. 13 is a plan view taken substantaillyin the optical-axis direction.

Employed herein are four pieces of fiber exit portions 35 a, 35 b, 35 c,35 d as a means for creating an arbitrary light quantity distribution onthe Fourier transform plane 50. The respective fiber exit portions arein discrete positions eccentric from the optical axis AX and aredisposed at substantially equal distances from the optical axis AX.Turning to FIGS. 12 and 13, the fiber exit portions 35 a, 35 b, 35 c, 35d are stretchable and contractible in the direction perpendicular to theoptical axis by means of drive elements such as motors and gears whichare incorporated into the movable members 36 a, 36 b, 36 c, 36 d throughsupport bars 37 a, 37 b, 37 c, 37 d. The movable members 36 a, 36 b, 36c, 36 d themselves are also movable in the circumferential directionabout the optical axis along a fixed guide 36 e. Therefore, theindividual fiber exit portions 35 a, 35 b, 35 c, 35 d are independentlymovable in the intra-plane direction vertical to the optical axis.Namely, these exit portions are independently movable to arbitrarypositions (so as not to overlap with each other). The respectivepositions (within the plane vertical to the optical axis AX) of thefiber exit portions 35 a, 35 b, 35 c, 35 d shown in FIGS. 12 and 13 arechanged preferably in accordance with the reticle patterns to betransferred. Exit surfaces of the exit portions 35 a, 35 b may be formedwith the light scattering members such as diffusion plates and withaperture spots for regulating the apertures.

The luminous flux distributing member may be replaced with the spatialfilter 16 provided in the vicinity of the Fourier transform plane. Inthis case, however, a loss of the light quantity increases.

Note that the foregoing luminous flux distributing means (such as theoptical fibers and the beam splitter) depicted in FIGS. 9 through 12 areall intended to prepare the light quantity distribution in closeproximity to the Fourier transform plane of the reticle patterns. Thepositions (conjugate relation) of the exit portions of the luminousdistributing means may be arbitrarily set.

Given is a case where the plural beams of illumination light come fromthe luminous flux distributing member. However, one luminous flux may beincident on the position eccentric by a predetermined quantity from theoptical axis AX on the Fourier transform plane. For instance, oneluminous flux may fall on the Fourier transform plane 50 by providingone exit portion of the fiber 35 shown in FIG. 12.

Now, the incident positions of the luminous flux distributing memberonto the Fourier transform plane are determined (changed) preferablyaccording to the reticle patterns to be transferred. A method ofdetermining the positions in this case is that, as explained referringto FIG. 40, the incident position (incident angle ψ) of the illuminationluminous fluxes from the exit portions to the reticle patterns may beset to obtain the effects of improving the resolving power and focaldepth which are optimal to the degree of fineness (pitch) of thepatterns to be transferred.

By exemplifying a case where the optical fibers are used herein as aluminous flux transform member, there will be next explained a concreteexample of determining the position (gravity position of the lightquantity distribution created by one luminous flux incident on theFourier transform plane) of the luminous flux passing above the Fouriertransform plane. The explanation will be given with reference to FIGS.15A through 15D. FIGS. 15A to 15D are diagrams schematicallyillustrating the exit surfaces of the elements from the exit portions 35a, 35 b to the reticle patterns 28. The exit surfaces coincide with theFourier transform plane 50. At this time, the lenses or a lens group forbringing both of them into a Fourier transform relation are expressed inthe form of a single lens 26 FIG. 14. Further, it is assumed that f isthe distances from the principal point on the side of the fly eye lensto the exit surface and from the principal point on the side of thereticle of the lens 26 to the reticle patterns 28.

FIGS. 15A and 15C are diagrams each showing an example of some patternsformed in the reticle patterns 28. FIG. 15B illustrates the centralposition (the optimum position of a peak value of the light quantitydistribution on the Fourier transform plane) on the Fourier transformplane (or the pupil plane of the projection optical system) which isoptimal to the reticle patterns of FIG. 15A. FIG. 15D is a diagramillustrating the central position (gravity position of the lightquantity distribution created by one luminous flux incident on theFourier transform plane) of the exit portions optimal to the reticlepatterns of FIG. 15C. FIG. 15A depicts so-called one-dimensionalline-and-space patterns wherein the transmissive portions and lightshielding portions are arranged with equal widths to assume a stripedconfiguration in the direction Y and also regularly arranged at pitchesP in the direction X. At this time, the central position of one exitportion (surface illuminant) is, as illustrated in FIG. 15B, in anarbitrary position on a line segment Lα or Lβ in the direction Y whichis presumed within the Fourier transform plane. FIG. 15B is a diagramshowing a Fourier transform plane 50A associated with the reticlepatterns 28 which is viewed substantially in the optical-axis directionAX. Coordinate systems X, Y within the Fourier transform plane 50A areidentical with those in FIG. 15, wherein the reticle patterns 28 areobserved in the same direction. Now, the distances α, β from the centerC through which the optical axis AX passes to the respective linesegments Lα, Lβ have a relation such as α=β. These distances are equalsuch as: α=β=f·(1/2)·(λ/P), where λ is the exposure wavelength. When thedistances α, β are expressed as f·sin ψ, sin ψ=λ/2P. This is identicalwith the numerical value explained in FIG. 40. Hence, the plurality ofexit portions are provided, and the respective central positions of theindividual exit portions are on the line segments Lα, Lβ. On thisassumption, it follows that the two diffracted light components i.e.,the 0th-order diffracted light component generated from the illuminationlight coming from the respective exit portions and any one of the (±)primary diffracted light components pass through the position havingalmost equal distances from the optical axis AX on the pupil plane 51 ofthe projection optical system with respect to the line-and-spacepatterns. Therefore, as discussed above, the focal depth with respect tothe line-and-space patterns (FIG. 15A) can be maximized, and the highresolving power is also obtainable. Note that one exit portion (surfaceilluminant) to be formed on the line segments Lα, Lβ may suffice if apositional deviation concomitant with the defocus of the wafer 30 isignored.

Next, FIG. 15C shows a case where the reticle patterns are so-calledisolated spatial patterns, wherein Px is the X-directional (crosswise)pitch of the patterns, and Py is the Y-directional (vertical) pitchthereof. FIG. 15D is a diagram illustrating the optimum position of theexit portion in that case. The positional/rotational relationshipassociated with FIG. 15C are the same as those of FIGS. 15A and 15B. Asseen in FIG. 15C, when the illumination light falls on thetwo-dimensional patterns, the diffracted light components are generatedin the two-dimensional directions corresponding to periodicity (X:Px,Y:Py) in the two-dimensional directions of the patterns. Even in thetwo-dimensional patterns shown in FIG. 15C, if the 0th-order diffractedlight component and any one of the (±) primary diffracted lightcomponents in the diffracted light have almost equal distances from theoptical axis AX on the projection optical system pupil plane 51, thefocal depth can be maximized. In the patterns of FIG. 15C, theX-directional pitch is Px. Therefore, as shown in FIG. 15, if thecenters of the respective exit portions are on the line segments Lα, Lβdefined such as α=β=f·(1/2)·(λ/Px), the focal depth can be maximizedwith respect to the X-directional elements of the patterns. Similarly,if the centers of the respective exit portions are on line segments Lγ,Lε defined such as γ=ε=f·(1/2)·(λ/Py), the focal depth can be maximizedwith respect to the Y-directional elements of the patterns.

When the illumination luminous fluxes corresponding to the exit portionsdisposed in the respective positions shown thus in FIGS. 15B and 15D areincident on the reticle patterns 28, the 0th-order diffracted lightcomponent Do and any one of a (+) primary diffracted light component Dpand a (−) primary diffracted light component Dm pass through the lightpaths having the equal distances from optical axis AX on the pupil plane51 within the projection optical system 29. Consequently, as stated inconjunction with FIG. 4, it is possible to actualize a projection typeexposure apparatus with a high resolving power and a large focal depth.Only two examples of the reticle patterns 28 shown in FIGS. 15A and 15Bhave been considered so far. Even in other patterns, however, theattention is paid to the periodicity (degree of fineness) thereof. Therespective exit portions may be disposed in such positions that twoluminous fluxes i.e., the 0th-order diffracted light component and anyone of the (+) primary diffracted light component and the (−) primarydiffracted light component travel through the light paths having thesubstantially equal distances from the optical axis AX on the pupilplane 51 within the projection optical system. Provided in the patternexamples of FIGS. 15A and 15C are the patterns having a ratio (dutyratio), 1:1, of the line portion to the spatial portions. Consequently,(±) primary diffracted light components become intensive in thediffracted light generated. For this reason, the emphasis is placed onthe positional relation between one of the (±) primary diffracted lightcomponents and the 0th-order diffracted light component. In the case ofbeing different from the duty ratio of 1:1, however, the positionalrelation between other diffracted light components, e.g., one of (±)secondary diffracted light components and the 0th-order diffracted lightcomponent may be set to give the substantially equal distances from theoptical axis AX on the projection optical system.

If the reticle patterns 28, as seen in FIG. 15D, contain thetwo-dimensional periodic patterns, and regarding one specific 0th-orderdiffracted light component, there probably exist higher-order diffractedlight components including the primary diffracted light components ofwhich the order is higher than the 0th-order diffracted light component,which are distributed in the X-direction (the first direction) and inthe Y-direction (the second direction) about the single 0th-orderdiffracted light component on the pupil plane 51 of the projectionoptical system. Supposing that the image of the two-dimensional patternsis formed well with respect to one specific 0th-order diffracted lightcomponent, the position of the specific 0th-order diffracted lightcomponent may be adjusted so that three light components i.e., one ofthe higher-order diffracted light components distributed in the firstdirection, one of the higher-order diffracted light components and onespecific 0th-order diffracted light component are distributed at thesubstantially equal distances from the optical axis AX on the pupilplane 51 of the projection optical system. For instance, the centralposition of the exit portion in FIG. 15D is arranged to coincide withany one of points Pξ, Pη, Pκ, Pμ. The points Pξ, Pη, Pκ, Pμ are allintersections of the line segment Lα or Lβ (the optimum position to theX-directional periodicity, i.e., the position in which the 0th-orderdiffracted light component and one of the (±) primary diffracted lightcomponents in the X-direction have the substantially equal distancesfrom the optical axis on the pupil plane 51 of the projection opticalsystem) and line segments, Lγ, Lε (the optimum positions to theY-direction periodicity). Therefore, those positions are the lightsource positions optimal to either the pattern direction X or thepattern direction Y.

Presumed in the above-described arrangement are the patterns astwo-dimensional patterns having the two-dimensional directivities at thesame place on the reticle. The aforementioned method is applicable to acase where a plurality of patterns having different directivities existin different positions in the same reticle patterns.

Where the patterns on the reticle have the plurality of directivitiesand degrees of fineness, the optimum position of the secondaryilluminant image, as explained earlier, corresponds to the respectivedirectivities and degrees of fineness of the patterns. Alternatively,however, the secondary illuminant image may be in the averaged positionof the respective optimum positions. Besides, this averaged position mayalso undergo load averaging in which a weight corresponding to thesignificance and degree of fineness of the pattern is added.

(One of or a plurality of) luminous fluxes with which the reticle 27 isirradiated are incident on the reticle 27 with an inclination to theoptical axis AX of the projection optical system 29. At this time, ifthe direction of the light quantity gravity of those illuminationluminous fluxes is inclined to the optical axis AX, there arises such aproblem that the position of a transferred image shifts in theintra-wafer-surface direction during minute defocusing of the wafer 30.To prevent this problem, the direction of the light quantity gravity ofthe illumination luminous fluxes distributed on the Fourier transformplane is made perpendicular to the reticle patterns 28, i.e., parallelto the optical axis AX. For example, where the optical fibers areemployed as a luminous flux transform member, the arrangement iseffected to make zero a vector sum (integration) of a product of theexit portion's position (positional vector within the Fourier transformplane from the optical axis AX of the gravity of the light quantitydistribution created by the exit portions) and the transmission lightquantity. Note that when using the diffraction grating pattern plate 12as a member for forming the light quantity distribution on the Fouriertransform plane, this condition is automatically satisfied. Thefollowing is a definite example of the above-mentioned distribution ofthe illumination light quantity. The number of luminous fluxes is set to2m (m is the natural number), and positions of the m-number luminousfluxes are arbitrarily set, while positions of remaining m-numberedluminous fluxes may be set in symmetry with respect to the optical axisAX and the former m-numbered luminous fluxes as well.

Besides, the exit surfaces of the exit portions 35 a, 35 b may be formedwith aperture stops for regulating the apertures and with lightscattering members such as diffusion plates, etc.

The number of the plurality of the exit portions is not limited to 4 butmay be arbitrarily set corresponding to the reticle patterns 28. Forinstance, three pieces of exit portions are available. The center of asingle piece of secondary illuminant image formed by one exit portion isset in the position eccentric by a quantity corresponding to the reticlepatterns 28 from the optical axis AX. The secondary illuminant image maybe changed depending on the time.

In addition, if necessary, the reticle 27 may be arranged so as not toundergo an irradiation of the illumination light from a specific one ofthe exit portions. For example, supposing that a broken line circle 50Ain FIG. 13 is formed corresponding to a size of the pupil plane 51 ofthe projection optical system 29, the light shielding member is providedoutwardly of this broken line circle 50A in combination with the Fouriertransform plane 50 (FIG. 1) of the illumination system. When theunnecessary exit portions retreat to this light shielding portion(outside the broken line circle 50A of FIG. 13), it is possible toobtain a desired number of exit portions.

A diameter (numerical aperture of one beam of illumination light on theFourier transform plane of the illumination system) of opening of eachexit portion is preferably set so that a so-called 6-value (a ratio ofthe numerical aperture of the illumination optical system which isestimated in the projection optical system to the numerical aperture ofthe projection optical system) becomes approximately 0.1 to 0.3 perluminous flux. If the σ-value is 0.1 or under, the image fidelitydeclines, whereas if this value is 0.3 or above, the increasing effectof the focal depth is reduced.

FIG. 16 is a diagram schematically illustrating a construction of theprojection type exposure apparatus in accordance with a secondembodiment of this invention. The principal configuration of the aligneris the same as that of FIG. 1. The same members as those in FIG. 1 aremarked with the same reference numbers. In this embodiment, the meansfor forming an arbitrary light quantity distribution on the Fouriertransform plane involves the use of a movable optical member such as areflection mirror and the like in place of the luminous fluxdistributing member used in the first embodiment.

The lens system 4 is irradiated with a luminous flux L1 emitted from thelight source 1 via the elliptical mirror 2. The luminous flux L1 isshaped into a substantially collimated luminous flux L2 by means of thelens system 4 and becomes a luminous flux L3 through the fly eye lens 7and the aperture stop 8. A reflector 54 is irradiated with the luminousflux L3 via the lens system 11. A field stop 20 is irradiated with aluminous flux L5 reflected by the reflector 54 through lens systems 15,19. Further, a half-mirror 24A is irradiated with a luminous flux L5passing through the field stop 20 via a lens system 22. The luminousflux L5 reflected by the half-mirror 24A then falls on the reticle 27 ata predetermined incident angle through a lens system (principalcondenser lens) 26. The configuration towards the wafer from the lenssystem 26 is the same as that of FIG. 1 (the first embodiment), and thedescription is therefore omitted. Note that the aperture stop 8 is astop for determining a coherent factor σ of the illumination luminousflux as in the first embodiment.

On the other hand, the luminous flux penetrating the half-mirror 24A iscondensed by a lens system 56 and undergoes a photoelectric conversionin a light quantity meter 57 such as a semiconductor sensor and thelike. A light quantity signal S obtained from the light quantity meter57 is transmitted as an electric signal to a control circuit 58. Basedon the light quantity signal S, the control circuit 58 givesinstructions to a shutter drive unit 53 for driving a shutter 52 and todrive elements 55A, 55B for driving the reflector 54. When the shutterdrive unit 53 is operated, the luminous flux 2 is cut off by the shutter52, thereby stopping the exposure. Note that this embodiment has aconstruction to control the shutter drive unit 53 and the drive elements55A, 55B by use of the light quantity meter 57. The effects of thepresent invention are not varied by the arrangement that the control isperformed simply in accordance with the exposure time without providingthe light quantity meter 57.

Based on the construction given above, the incident surface of the flyeye lens 7, the field stop 20, the reticle patterns 28 (patternsurfaces) of the reticle 27 and the wafer 30 are conjugate to eachother. Further, the exit surface of the fly eye lens 7, the Fouriertransform plane 50 of the reticle 27 and the pupil plane 51 of theprojection optical system 29 are also conjugate to each other.

Note that for making the illuminance on the reticle surface 27homogeneous, the incident surface of the fly eye lens 7 is positioned tohave an image forming relation with the reticle 27. On the other hand,the exit surface of the fly eye lens 7 is positioned corresponding tothe Fourier transform plane (pupil plane) with the reticle patterns 28of the reticle 27 serving as object surfaces.

The reflector 54 is, as described above, in the position substantiallyconjugate to the reticle 27 and rotatable about two axes orthogonal toeach other on, e.g., a reflecting surface. the reflector 54 is rotatedby the drive elements 55A, 55B such as motors, piezoelements and thelike.

In FIG. 16, the reflected light L5 is shown by a solid line. Thereflected luminous flux L5 is allowed to travel in the direction of,e.g., a luminous flux L4 by changing a rotary angle of the reflector 54.That is, one secondary illuminant image at the exit end of the fly eyelens 7 is shifted on the Fourier transform plane 50. It is also, as amatter of course, possible to provide a component movable in thedirection perpendicular to the sheet of FIG. 16.

In the thus constructed exposure apparatus, the reflector 54 is drivenby the drive elements 55A, 55B and set in predetermined positions.Thereupon, the luminous flux L3 whose principal beam is coaxial with theoptical axis AX of the illumination optical system is changed intoluminous fluxes L5, L4 whose principal beams are inclined to the opticalaxis AX. These luminous fluxes L5, L4 are condensed respectively inpositions different from the optical axis AX in the vicinity of theFourier transform plane 50 of the reticle 27. For this reason, aluminous flux L5 with which the reticle 27 is irradiated is obliquelyincident on the reticle 27. As explained in FIG. 40, the high resolvingpower and the large focal depth are attainable. Turning to FIG. 16supposing that an illumination luminous flux L5 for illuminating thereticle 27 is always incident on the reticle 27 at a constant incidentangle, however, the light quantity gravity (in other words, theprincipal beam of the luminous flux L5) in the incident direction of theluminous flux L5 by which the image is formed on the wafer 30 comes toassume a slant state (non-telecentric state) to the wafer 30. Namely, itmay happen that the image position deviates sideways within the wafersurface with a minute deviation (defocus) of the wafer 30 in thedirection of the optical axis AX. Taken in this embodiment is such ameasure for preventing this lateral deviation that the incident angle ofthe illumination luminous flux on the reticle 27 is changed by thereflector 54. Hence, after performing the illumination with apredetermined amount of exposure by use of the luminous flux L5 incidentat a certain incident angle ψ, the reflector 54 is moved. Theillumination is effected this time to have the same amount of exposureas the above-mentioned by using the luminous flux incident at anincident angle −ψ. The lateral deviation of the light quantity gravityincident on the wafer from a normal line of the wafer surface is therebyoffset with the exposure at incident angle +ψ and the exposure at theincident angle −ψ. The projection type exposure apparatus in thisembodiment is provided with the light quantity meter 57 for measuringthe quantity of light with which the reticle is irradiated. It istherefore feasible to easily make constant the exposure quantity at theincident angle +ψ and the exposure quantity at the incident angle −ψ andfurther equalize these values. Even in the case of controlling theexposure time instead of providing the light quantity meter, it issimilarly possible to make the respective exposure quantities constantand equalize these values. An arbitrary light quantity distribution onthe Fourier transform plane 50 can be formed in this manner by use ofthe movable reflector.

In accordance with this embodiment, the reflector 54 defined as amovable optical member existing in the position substantially conjugateto the reticle 27 is moved. It can be therefore considered that if thefield stop 20 is disposed closer to the light source than the reflector54, a positional relation between the reticle 27 and the field stop 20,though small, deviates with the movement of the reflector 54. Hence, thefield stop 20 is desirably is placed closer to the reticle 27 than thereflector 54.

If there is an insufficient compensation of chromatic aberration of theoptical elements in the projection optical system 29 and theillumination optical system (from the lens system 26 to the light source1 in the Figure), a wavelength selecting element such as a band-passfilter is used in the illumination luminous flux, e.g., the luminousflux L2. Alternatively, the reflection member such as the ellipticalmirror 2 may involve the use of a multilayer dielectric mirror toenhance a reflectivity of only the specific wavelength.

It is to be noted that even in the case of transferring circuit patternsby the projection type exposure apparatus in this embodiment, as in thefirst embodiment, the ratio, i.e., a so-called coherent factor σ, of thenumerical aperture of the illumination luminous flux to the numericalaperture on the part of the photo mask of the projection optical systemis preferably 0.1 to 0.3. Hence, the fly eye lens 7 and the aperturestop 8 are set so that σ=0.1 to 0.3.

FIG. 17 is a diagram depicting a configuration of a variant form 1 ofthe projection type exposure apparatus in this embodiment. This variantform employs a lens system as a movable optical member. However, theconstructions toward the light source from the fly eye lens 7 and towardthe reticle from the Fourier transform plane (pupil plane of theillumination optical system) 50 are the same as those in FIG. 16, andthe description is therefore omitted. The luminous flux emerging fromthe fly eye lens falls on a lens system 59 a having a positive power viathe lens system 11 on a lens system 59 b having a negative power. Thelens systems 59 a, 59 b are disposed in close proximity to the surfaceconjugate to the reticle 27. A sum of the powers of the lens systems 59a, 59 b becomes 0. The lens systems 59 a, 59 b are movable respectivelyby the lens drive members 55 c, 55 d within the surface vertical to theoptical axis AX. The luminous flux penetrating the lens systems 59 a, 59b movably by the drive members 55 c, 55 d becomes a luminous flux havingthe principal beam different from the optical axis AX of theillumination optical system. The luminous flux is condensed in aposition different from the optical axis AX on the Fourier transformsurface 50.

Referring to FIG. 17, the lens systems 59 a, 59 b are moved almost anequal distance in opposite directions prependicular to the optical axis.As a result, the luminous flux penetrating the lens systems 59 a, 59 bis incident on the lens system 15 at a given angle inclined to theoptical axis AX. If the positions of the glens systems 59 a, 59 b arechanged by the lens drive members 55 c, 55 d, the luminous flux exitedcan be oriented in an arbitrary direction. Note that the lens drivemembers 55 c, 55 d are controlled by a control circuit 58.

A new lens system having a positive power is disposed closer to thereticle 27 than the lens system 59 b and movably by the lens drivemember. Further, a total of powers of the lens systems 59 a, 59 b and ofthe newly added lens system having the positive power may be arranged tobe 0. Similarly, a lens system having a negative power is disposedcloser to the light source than the lens system 59 a. A total of powersof the lens systems 59 a, 59 b and of the newly added lens system havingthe negative power may be also arranged to be 0. Note that thearrangement of the lens system in which position is variable is notlimited to only the combinations given above. A permissible arrangementis that the lens group composed of a plurality of lens elements has apower total of 0, and the illumination luminous flux can be oriented inan arbitrary direction by moving the respective lens elements. The lenselements to be driven are not specified. Similarly, the lens elementscapable of orienting the illumination luminous flux in an arbitrarydirection are satisfactory.

FIG. 18 is a diagram schematically illustrating a second variant form ofthe projection type exposure apparatus in this embodiment. In thisvariant form, the movable optical element involves the use of a phototransmitting means such as fibers. An arbitrary light quantitydistribution is formed on the Fourier transform plane. However, theconstructions toward the light source from the fly eye lens 7 and towardthe reticle from the lens system 19 are the same as those in FIG. 16,and the description is therefore omitted. The Fourier transform plane 50is linked via the photo transmitting means such as optical fibers 60 tothe exit side of the fly eye lens 7. Hence, the exit surface of the flyeye lens 7 corresponds to the Fourier transform plane 50. The exit sideof the optical fibers 60, i.e., the portion on the side of the Fouriertransform plane 50, is movable by a drive member 55 e. The illuminationluminous flux (illuminant image) can be thereby distributed in arbitrarypositions within the Fourier transform plane 50. The drive member 55 eis, as in the same way with the variant form 1 of this embodiment,controlled by the control circuit 58.

Next, an exposure method by use of the exposure apparatus in the secondembodiment will be described with reference to FIGS. 19A and 19B.

FIGS. 19A and 19B are flowcharts each showing the exposure method in theembodiment of this invention. A difference between FIGS. 19A and 19Blies in whether the exposure is stopped or not when driving thereflector 54. In advance of the exposure, the shutter 52 is in such astatus as to cut off the luminous flux L2. Determined herein are thenumber of positional changes of the reflector 54, coordinates of therespective positions of the reflector and exposure quantities for therespective coordinates (step 101). As stated before, however, if aso-called light quantity gravity of the illumination light when theluminous flux L5 corresponding to each position of the reflector 54falls on the reticle 27 deviates from the optical axes AX of theillumination optical system and the projection optical system 29, thereexists a possibility of causing a lateral deviation of the transferredimage due to a very small defocus of the wafer 30. It is thus requiredto determine the respective positions of the reflector 54 and theillumination light quantities (exposure quantities) for illuminationaccording to the respective positions of the reflector 54 so that thelight quantity gravity coincides with the optical axis AX. This may beaccomplished by determining, when one pattern exposure is completed byeffecting 2m-time (m is the natural number) exposing processes, thecoordinates of the reflector 54 effecting the m-time exposures thereof.Further, the coordinates of the reflector effecting the remaining m-timeexposures may be set in symmetry with respect to the optical axis AX andthe incident luminous flux in a case where the incident luminous flux isassociated with the former m-time exposures. Incidentally, a method ofdetermining the coordinates of the reflector 54 which is performing theexposing processes at respective angles in a plurality of positions maybe prescribed so that the light quantity distribution (positionalcoordinates of the luminous fluxes) on the Fourier transform plane 50has the conditions explained in the first embodiment with reference toFIGS. 14 and 15. More specifically, the position of the reflector 54may, when transferring the patterns depicted in FIG. 15A, be determinedso that the center (principal beam) of the illumination luminous flux L5or L4 reflected by the reflector 54 coincides on the line segment Lα orLβ on the Fourier transform surface 50. When transferring the patternsshown in FIG. 15B, the central position of the illumination luminousflux reflected by the reflector 54 may be determined to coincide on theline segment Lα or Lβ and the line segment Lγ or Lε. The optimumposition in this case includes four points pξ, pη, pκ, pμ.

Next, operating instructions are issued from the control circuit 58 tothe drive members 55 a, 55 b, and the reflector 54 is set in apredetermined first position (step 102). The operator inputs the firstposition by means of an input unit incorporated into the control circuit58. Alternatively, the control circuit 58 is allowed to determine thefirst position of the reflector 54 on the basis of the information onthe circuit patterns 28 on the reticle 27, the information beinginputted by the operator through the input unit. A necessary totalexposure quantity E is likewise inputted by the operator through theinput unit. The control circuit 58 is, even when being inputted by theoperator, permitted to decide specific degrees of exposures which areeffected in the respective positions of the reflector 54. As in thefirst embodiment, the information described above may be obtained-byreading the bar codes BC provided on the mask.

Subsequently, the action enters the actual exposing process. Thereflector 54 is almost fixed in the first position previouslydetermined. In this state, the control circuit 58 issues an instructionof “Open shutter” to the shutter drive unit 53. A shutter 52 is opened,and the exposure is started (step 103). The reticle is illuminated withthe illumination luminous flux. Consequently, the reticle patterns 28are transferred on the wafer 30. At this moment, some illuminationluminous fluxes passing through the half-mirror 24A are received andconverted photoelectrically by the light quantity meter 57. When anintegrated value of the light quantity signal S thereof reaches apredetermined value, i.e., an exposure quantity corresponding to thepreviously determined first position (step 104), or just before reachingthat value, the control circuit 58 gives the operating instructions tothe drive members 55 a, 55 b. The position of the reflector 54 isthereby changed to a predetermined second position (step 105). Note thatwhen the integrated value (integrated light quantity) of the lightquantity signal S, as shown in FIG. 19B, reaches the predeterminedvalue, the shutter 52 is temporarily stopped (step 105 a). The reflector54 is moved after stopping the exposure. The reflector 54 issubstantially fixed in the predetermined position, and thereafter theshutter 52 is opened (step 105 b). Then, the exposure may resume.

When the integrated value of the light quantity signal S comes to thepredetermined value in the second position of the reflector 54 (step106), or just before reaching this value, the reflector 54 is moved inthe same manner as before. The reflector 54 is substantially fixed in athird position, and the exposure continues. At this time also, theshutter 52 is temporarily closed as in the previous case, and theexposure may be stopped.

Thereafter, the position of the reflector 54 is likewise changed tom-numbered positions, thus performing the exposures. When the integratedvalue of the light quantity signal S somes to the preset total exposurequantity E in the m-th position of the reflector 54 (step 107), theshutter 52 is closed, thus completing the exposure.

Incidentally, where E₁, E₂, . . . , E_(m)(ΣEi=E, 1≦i ≦m) are theexposure quantities in the respective positions, the exposure in thefirst position is ended when the integrated value of the light quantitysignal S reaches E₁ or just before reaching it. The exposure in thesecond position is ended when the integrated value reaches (E₁+E₂) orjust before reaching it. Namely, the exposure in the arbitrary n-thposition among the exposures in the first through m-th positions comesto an end when the integrated value reaches ΣEi (1≦i ≦n).

Adopted is a method of stopping the exposure by closing the shutter 52during a movement of the reflector 54. In this case, the integratedvalue is reset to 0 during a stoppage of the exposure. Thereafter, theexposure resumes, and when the integrated value of the light quantitysignal S reaches the predetermined value En, the exposure in thearbitrary n-th position may be ended.

The exposures in accordance with the second embodiment of this inventionare thus completed. Therefore, the wafer 30 is carried in parallelwithin the surface vertical to the optical axis AX by a wafer stage 31.The exposures may be newly effected in other exposure regions of thewafer 30. Besides, the exposures may be performed in the exposed regionby replacing the reticle 27 while superposing other circuit patternsthereon. Note that when newly effecting the exposures in other positionsof the wafer 30, the sequence of positions of the reflector 54 may be soreversed as to start with the m-th position and end up with the firstposition.

Based on the above-described exposure method, the reflector 54 is movedwhile making the exposure continue. In this case, the illumination lightemerging from directions other than the predetermined one is incident onthe reticle 27 during the movement of the reflector 54. This causes apossibility where the effects to obtain the foregoing high resolvingpower and large focal depth will decline. For preventing this, a spacefilter having transmissive portions only in predetermined positions isprovided in the vicinity of the Fourier transform plane 50 between thelens systems 15, 19 shown in FIG. 16. In this spatial filter, thetransmissive portions are formed in the predetermined positionseccentric from the optical axis AX on the Fourier transform plane 50,while the light shielding portions are formed in other positions. Thepredetermined positions of the transmissive portions are those throughwhich the illumination luminous fluxes L5, L4 generated from thereflector 54 in the respective positions for obtaining the desiredresolving power and focal depth pass above the Fourier transform plane50. Diameters of the respective transmissive portions serve to determineσ-values of the individual illumination luminous fluxes. Hence, thisdiameter is optically equivalent to the aperture stop 8 on the surfaceof the exit side of the fly eye lens 7 which has been previouslydetermined; viz., the diameter is set considering a relation inmagnification between the surface (conjugate to the Fourier transformplane 50) on the exit side of the fly eye lens 7 and the Fouriertransform plane 50. The diameter of the specific transmissive portionmay be smaller than the above-mentioned (equivalent) diameter. Namely,the σ-value of the specific luminous flux among the luminous fluxesincident on the reticle 27 may be decreased.

A light scattering member such as a lemon skin filter and the like maybe provided on the Fourier transform plane 50. This light scatteringmember is capable of making unsharp defects and dusts on the movableoptical member. It is therefore possible to prevent the unevenness ofilluminance on the reticle 27 which is caused by the dusts and defects.Note that an image forming relation between the reticle 27 and themovable optical member (reflector 54) becomes unsharp due to the lightscattering member but does not exert any adverse influence on theeffects of the present invention.

A third embodiment of the present invention will next be explained withreference to the drawings. In accordance with the first and secondembodiment described above, the luminous flux transform member forforming an arbitrary light quantity distribution on the Fouriertransform plane and the movable optical member are interposed betweenthe reticle and the optical integrator of the fly eye lens or the like.In this embodiment, however, the luminous flux transform member and themovable optical member are interposed between the optical integrator andthe light source, thereby improving the illuminance homogenizing effect.

FIG. 20 illustrates an outline of a projection type exposure apparatus(stepper) suitable for the third embodiment of this invention. Providedis a diffraction grating pattern plate 12 as an optical member (a partof an input optical system of this invention) for concentrating theillumination light on a light-source-side focal surface 72 a of a flyeye lens 72. Note that the same members as those in the first and secondembodiments are marked with the like symbols.

The illumination luminous fluxes emerging from the mercury lamp 1 arecondensed at a second focal point of the elliptical mirror 2.Thereafter, the diffraction grating pattern plate 12 is irradiated withthe condensed luminous flux via a mirror 6 and a lens system 71 of arelay system. An illumination method at this time may be the Kohlerillumination method or the critical illumination method. However, thecritical illumination method is desirable in terms of obtaining a moreintensive light quantity. The diffracted light generated from thediffraction grating pattern plate 12 is incident in concentration on theposition eccentric from the optical axis AX of the light-source-sidefocal surface 72 a (incident surface) of the fly eye lens 72 with theaid of the relay lens 73. It is herein assumed that the 0th-order and(±) primary diffracted light components are generated. At this moment,the light-source-side focal surface 72 a of the fly eye lens 72 and thediffraction grating pattern plate 12 have substantially a Fouriertransform relation through the relay lens 73. Note that the illuminationlight on the diffraction grating pattern plate 12 is illustrated ascollimated luminous fluxes in FIG. 20, but they are actually divergentluminous fluxes. Hence, the luminous flux incident on thelight-source-side focal surface 72 a of the fly eye lens 72 has acertain magnitude (thickness). Correspondingly, the exit luminous fluxfrom a reticle-side focal surface 72 b of the fly eye lens 72 inaccordance with the incident light flux on the light-source-side focalsurface 72 a also has a certain magnitude.

On the other hand, the reticle-side focal surface 72 b of the fly eyelens 72 is so disposed as to be substantially coincident with theFourier transform plane (pupil conjugate plane) of the reticle patterns28.

The respective lens elements of the fly eye lens 72 depicted in FIG. 20are double convex lens elements, shown therein is a case where thelight-source-side focal surface 72 a coincides with the incidentsurface, and the reticle-side focal surface 72 b coincides with the exitsurface. The lens elements of the fly eye lens do not strictly fulfillthis relationship. Those lens elements may be plane-convex lenselements, convexo-plane lens elements or plane-concave lens elements.The fly eye lens is composed of one or more lens elements.

Note that the light-source-side focal surface 72 a of the fly eye lens72 and the reticle-side focal surface 72 b have, as a matter of course,the Fourier transform relation. Hence, in the example of FIG. 1, thereticle-side focal surface 72 b of the fly eye lens 72, i.e., the flyeye lens exit surface, has the image forming (conjugate) relation withthe diffraction grating pattern plate 12.

Now, the reticle 27 is illuminated to have a homogeneous illuminatingdistribution with the luminous flux emerging from the reticle-side focalsurface 72 b of the fly eye lens 72 via condenser lenses 74, 75 and amirror 24. In accordance with this embodiment, the spatial filter 16composed of a metal plate or the like and bored with two openingscorresponding to the (±) primary diffracted light components from thediffraction grating pattern plate 12 is disposed in the vicinity of thereticle-side focal surface 72 b (exit side) of the fly eye lens 72. The0th-order diffracted light component from the diffraction gratingpattern plate 12 is thereby cut off. The illumination light with whichthe reticle patterns 28 are illuminated are therefore limited to the onehaving two secondary illuminant images in the positions eccentric fromthe optical axis AX on the reticle-side focal surface 72 b of the flyeye lens 72. The diffraction grating pattern plate 12 is employed as anoptical member for concentrating the illumination light on thelight-source-side focal surface 72 a of the fly eye lens 72. Formed arethe two secondary illuminant images symmetric with respect to theoptical axis AX. Hence, the illumination light with which the reticlepatterns 28 are illuminated is limited to only the luminous fluxeshaving specific incident angles on the reticle patterns 28. As discussedabove, the image of the diffraction grating pattern plate 12 is formedon the reticle-side focal surface 72 b of the fly eye lens 72. Thereticle-side focal surface 72 b and the reticle pattern surfaces 28 havethe Fourier transform surface relation. This eliminates suchpossibilities that the image of the diffraction grating pattern plate 12itself is formed on the reticle 27 to deteriorate the illuminancehomogeneity, and further there is produced the ununiformity due to dustand the defects of the diffraction grating pattern plate 12. Note thatthe spatial filter 16 is provided in close proximity to thelight-source-side focal surface 72 b of the fly eye lens 72, i.e., onthe side of the exit surface of the fly eye lens 72; but this filter maybe provided on the surface 72 a, i.e., on the side of the incidentsurface.

The diffracted light generated from the reticle patterns 28 on the thusilluminated reticle 27 is, as in the same way explained with referenceto FIG. 40, condensed and image-formed by the telecentric projectionoptical system 29. The image of the reticle patterns 28 is transferredon the wafer 30.

The diffraction grating pattern plate 12 may be not only thetransmissive pattern plate similar to that in the first embodiment butalso a reflective pattern plate. If the diffraction grating patternplate 12 exhibits a reflective property, as illustrated in FIG. 21, areflective diffraction grating pattern plate 12A is, as depicted in FIG.8, illuminated with the illumination luminous flux from the relay lens71. The diffracted light reflected and diffracted therein may beincident on the fly eye lens 72. The constructions toward the lightsource from the relay lens 71 and toward the reticle from the fly eyelens 72 are the same as those of FIG. 20. At this time, as in the firstembodiment, the incident directions and incident angles of theillumination luminous fluxes (plural) incident on the reticle patterns28 of the reticle 27 are determined depending on the reticle patterns28. The incident directions and angles are arbitrarily adjustable bychanging directivities and pitches of the diffraction grating patternplates 12, 12A. For instance, diffraction grating plates 12, 12A, arereplaced with those having different pitches, thereby making variablethe illumination light incident on the light-source-side focal surface72 a of the fly eye lens 72 and further making variable a distance ofthe secondary illuminant image from the optical axis AX on thereticle-side focal surface 72 b of the fly eye lens 72. It is thereforefeasible to make variable the incident angle of the illumination lighton the reticle patterns 28 of the reticle 27. As in the firstembodiment, when the diffraction grating pattern plates 12, 12A are maderotatable (e.g., through 90°) in an arbitrary direction within thesurface vertical to the optical axis AX, it is possible to correspond tothe case where the pitch direction of the line-and-space patterns of thereticle patterns 28 is different from the directions x, y. Further, therelay lens 73 may come under a zoom lens system (such as an afocal zoomexpander, etc.) consisting of a plurality of lens elements, and thecondensing position can be varied by changing the focal distance. Atthis time, however, it is required to keep substantially the Fouriertransform relation between the diffraction grating pattern plate 12 or12A and the light-source-side focal surface 72 a of the fly eye lens 72.The optical member for concentrating the illumination light on thelight-source-side focal surface 72 a of the fly eye lens 72 describedabove is not limited to the diffraction grating pattern plate 12 or 12A.

As depicted in FIG. 22, the movable optical member shown in the secondembodiment, e.g., a movable plane mirror 54 is disposed instead of thereflective diffraction grating pattern plate 12A illustrated in FIG. 21.Provided also is a drive member 55 a such as a motor for making theplane mirror 54 rotatable. The plane mirror 54 is rotated or oscillatedby the drive member 55 a. The illumination light is incident on thelight-source-side focal surface 72 a of the fly eye lens 72, whereby thesecondary illuminant image of the reticle-side focal surface 72 b of thefly eye lens 72 can be varied according to the time. If the plane mirror54 is rotated to a plurality of proper angular positions during theexposing process, the secondary illuminant image of the reticle-sidefocal surface 72 b of the fly eye lens 72 can be formed in arbitraryconfigurations. Note that when using this type of movable reflectionmirror 54, the relay lens system 73 may be omitted. By the way, thespatial filter 16 depicted in FIG. 22 is provided on the side of theincident surface of the fly eye lens 72 but may be, as in the same waywith FIG. 20, provided on the side of the exit surface.

The optical member for concentrating the illumination light on thelight-source-side focal surface 72 a of the fly eye lens 72 may involvethe use of the beam splitter shown in FIG. 11, the optical fibers ofFIGS. 12 and 19, the prism of FIG. 9, the plurality of mirrors of FIG.10 and the optical member of FIG. 17.

FIG. 23 is a schematic diagram wherein an optical fiber bundle 35 isemployed. The constructions toward the light source from the relay lens71 and toward the reticle from the fly eye lens 72 are the same as thoseshown in FIG. 20. Respective exit portions 35 a, 35 b of the opticalfiber bundle 35 are disposed in positions corresponding to the reticlepatterns 28 in the vicinity of the light-source-side focal surface 72 aof the fly eye lens. At this time, lenses (e.g., field lenses) may beinterposed between the respective exit portions 35 a, 35 b of theoptical fiber bundle 35 and the fly eye lens 72. Further, there may begiven the Fourier transform relation between the light-source-side focalsurface 72 a of the fly eye lens and the light exit surfaces of theoptical fiber exit portions 35 a, 35 b owing to the lenses interposedtherebetween. As in the first embodiment, the respective exit portions(or the lenses between the exit portions 35 a, 35 b and the fly eye lens72) are made movable one-dimensionally or two-dimensionally within thesurface perpendicular to the optical axis by means of the drive membersuch as a motor, etc. The illumination light incident on thelight-source-side focal surface of the fly eye lens is thereby madevariable. The secondary illuminant image on the reticle-side focalsurface 72 b of the fly eye lens is also made variable.

FIG. 24 shows an example of using a prism 33 having a plurality ofrefraction surfaces as an optical member for concentrating theillumination light on the light-source-side focal surface 72 a of thefly eye lens 72. The illumination luminous fluxes can be incident on thelight-source-side focal surface 72 a of the fly eye lens 72 inaccordance with refraction angles of the prism 33. The constructionstoward the light source from the relay lens 71 and toward the reticlefrom the fly eye lens 72 are the same as those of FIG. 20. The incidentposition of the illumination luminous flux incident on thelight-source-side focal surface 72 a of the fly eye lens is madevariable by replacing the prism 33. In place of the prism 33, areflection mirror having differently-angled reflection surfaces is usedand, as illustrated in FIG. 22, disposed, thereby eliminating thenecessity for the drive member 55 a. The device, as a matter of course,incorporates a function to exchange the prism and the like. Whenemploying this type of prism also, the relay lens system 73 may beomitted.

FIG. 25 shows an example where a plurality of mirrors 34 a-34 d are usedas optical members for condensing the illumination light on thelight-source-side focal surface 72 a of the fly eye lens 72. Theconstructions toward the light source from the relay lens 71 and towardthe reticle from the fly eye lens 72 are the same as those of FIG. 20.Provided in the respective mirrors 34 a-34 d are position adjustingmechanisms and mechanisms for adjusting an angle of rotation about theoptical axis AX by which a illumination light quantity distribution onthe light-source-side focal surface 72 a of the fly eye lens 72 is madearbitrarily variable. Besides, the prism 33 may be combined with themovable plane mirror 54 or with the mirrors 34 a-34 d.

Further, the optical member for concentrating the illumination light onthe light-source-side focal surface 72 a of the fly eye lens 72 may bereplaced with the spatial filter 16 provided in the vicinity of thelight-source-side focal surface 72 a of the fly eye lens. The componentsin the embodiments shown in FIGS. 20 through 25 may be combined with thespatial filter 16. At this time, the number of openings of the spatialfilter 16 is not 1 but may be arbitrary numbers corresponding to thereticle patterns 28.

FIG. 26 is a diagram depicting a construction of the projection typeexposure apparatus in a further embodiment of this invention. The mirror24, the condenser lens 75, the reticle 27 and the projection opticalsystem 29 are the same as those shown in FIG. 20. As a constructiontoward the light source from the fly eye lens 72, any one of theexamples shown in FIGS. 20 through 25 and the example in which thespatial filter 16 is provided in the vicinity of the light-source-sidefocal surface 72 a of the fly eye lens 72 may be used. A spatial filter16A formed with arbitrary openings (transmissive portions, or furthersemitransmissive portions) is provided in close proximity to thereticle-side focal surface 72 b of the fly eye lens 72. The illuminationluminous flux emerging from the fly eye lens 72 is thereby regulated.The Fourier transform surface of a reticle-side focal plane 72 b of thefly eye lens 72 with respect to a relay lens 76A is defined as aconjugate plane to the reticle patterns 28, and hence a variable fieldstop (reticle blind) 76 is provided therein. The illumination luminousflux is Fourier-transformed again by the relay lens 76B and reaches aconjugate plane (Fourier transform plane) 50B of the reticle-side focalsurface 72B of the fly eye lens 72. The above-mentioned spatial filter16A may be provided on the Fourier transform plane 50B. The illuminationluminous flux from the fly eye lens 72 is further guided to the reticle27 with the aid of the condenser lenses 76C, 75 and the mirror 24. Notethat if there exists a system for condensing the illumination light onthe position eccentric by a quantity from the optical axis which isdetermined corresponding to the reticle patterns 28 on thelight-source-side focal surface 72A of the fly eye lens 72, the spatialfilter may not be disposed in the position of the optical member 16A or50B.

In this case also, the field stop (reticle blind) 76 is usable.

Shown is the example where the plural beams of illumination light comefrom the optical member for concentrating the illumination light on thelight-source-side focal surface 72 a of the fly eye lens 72 describedabove. However, one luminous flux may be incident on the positioneccentric by a predetermined quantity from the optical axis AX. Forexample, one exit portion of the fiber bundle 35 shown in FIG. 23 isprepared, while one luminous flux may be incident on thelight-source-side focal surface 72A of the fly eye lens 72.

In all the embodiments of FIGS. 20 through 26, a diameter of one openingof the spatial filters 16, 16A is desirably set so that a ratio, aso-called σ-value, of a numerical aperture for the reticle 27 associatedwith the illumination luminous fluxes penetrating the openings to areticle-side numerical aperture (NA_(R)) of the projection opticalsystem 29 is approximately 0.1 to 0.3.

For satisfying the condition of the σ-value determined by oneillumination luminous flux incident on the light-source-side focalsurface 72 a of the fly eye lens 72, a function to make the σ-valuevariable may be given to an optical member for concentrating theillumination light on the light-source-side focal surface 72 a of thefly eye lens and making variable a light quantity distribution in thevicinity of the focal surface 72 a in place of the spatial filter 16Adisposed close to the reticle-side focal surface 72 b of the fly eyelens 72. For instance, the spatial filter 16 is disposed on thelight-source-side focal surface 72 a of the fly eye lens, and theσ-value per luminous flux may be determined by the diameter of theopening thereof. Concomitantly, it is possible to further optimize theσ-value and NA in the form of the projection system by providing avariable aperture stop (NA regulating stop) in the vicinity of the pupil(incident pupil or exit pupil) 51 within the projection optical system29. The spatial filter 16 also exhibits an effect to shield unnecessaryluminous fluxes among the fluxes generated from the optical member forcondensing the illumination light on the light-source-side focal surface72 a of the fly eye lens 72. This filter further exhibits an effect toreduce the quantity of light which reaches the wafer by decreasing atransmissivity of the opening with respect to specific luminous fluxes.

It is preferable to determine (change) the incident position (positionof the secondary illuminant image on the light-source-side focal surface72 a of the fly eye lens 72) of (one or plural) illumination luminousflux(es) on the light-source-side focal surface 72 a of the fly eye lens72 in accordance with the reticle patterns to be transferred. In thiscase, the method of determining the position is that, as stated earlier,the incident position (incident angle ψ) of the illumination luminousflux from the fly eye lens 72 on the reticle patterns may be set toobtain the effect of improving the resolving power and focal depth thatare optimal to the degree of fineness (pitch) of the patterns to betransferred. A concrete example of the positional determination of thesecondary illuminant image (surface illuminant image) is the same as thedetermining method explained in the first embodiment with reference toFIGS. 14 and 15. It is assumed that the central position (the optimumposition of the gravity of the light quantity distribution created byone secondary illuminant image) of one secondary illuminant image is, asillustrated in FIG. 15B, on the Y-directional line segment Lα presumedwithin the Fourier transform plane. Alternatively, it is assumed thatthe centers of the respective secondary illuminant images are placed onarbitrary positions on the line segment Lβ, or, as illustrated in FIG.15D, on the line segments Lα, Lβ defined such as α=β=f·(1/2)·(λ/Px) oron the line segments Lγ, Lε defined such is γ=ε=f·(1/2)·(λ/Py). Based onthese assumptions, the focal depth can be maximized. As in the firstembodiment, the 0th-order diffracted light component Do coming from thereticle patterns 28 and any one of the (+) primary diffracted lightcomponent Dp and the (−) primary diffracted light component Dm may bearranged to pass through the light paths having equal distances from theoptical axis AX on the pupil plane 51 within the projection opticalsystem 29. If the reticle patterns 28, as seen in FIG. 15D, contain thetwo-dimensional periodic patterns, and when paying attention to onespecific 0th-order diffracted light component, there probably existhigher-order diffracted light components including the primarydiffracted light components of which the order is higher than the0th-order diffracted light component, which are distributed in theX-direction (the first direction) and in the Y-direction (the seconddirection) about the single 0th-order diffracted light component on thepupil plane 51 of the projection optical system. Supposing that theimage of the two-dimensional patterns is formed well with respect to onespecific 0th-order diffracted light component, the position of thespecific 0th-order diffracted light component may be adjusted so thatthree light components i.e., one of the higher-order diffracted lightcomponents distributed in the first direction, one of the higher-orderdiffracted light components distributed in the second direction and onespecific 0th-order diffracted light component are distributed atsubstantially equal distances from the optical axis AX on the pupilplane 51 of the projection optical system. For instance, the centralposition of the exit portion in FIG. 15D is arranged to coincide withany one of points Pξ, Pη, Pκ, Pμ. The points Pξ, Pη, Pκ, Pμ are allintersections of the line segment Lα or Lβ (the optimum position to theX-directional periodicity, i.e., the position in which the 0th-orderdiffracted light component and one of the (±) primary diffracted lightcomponents in the X-direction have substantially equal distances fromthe optical axis on the pupil plane 51 of the projection optical system)and line segments Lγ, Lε (the optimum positions to the Y-directionalperiodicity). Therefore, those positions are the light source positionsoptimal to either the pattern direction X or the pattern direction Y.

Note that in this embodiment, an arbitrary light quantity distributioncan be, as in the first embodiment, formed on the Fourier transformplane by controlling the luminous flux transform member and the movableoptical member on the basis of the information of bar codes and thelike.

A light scattering member such as a diffusion plate and an optical fiberbundle are provided in close proximity to the light-source-side focalsurface 72 a of the fly eye lens 11, thereby homogenizing theillumination light. Alternatively, the illumination light may behomogenized by employing an optical integrator such as a further fly eyelens (hereinafter referred to as the other fly eye lens) separately fromthe fly eye lens 72 used in the embodiments of the present invention. Atthis time, the other fly eye lens is disposed preferably closer to thelight source (lamp) 1 than the optical member e.g., the diffractiongrating pattern plate 12 or 12A shown in FIGS. 20 and 21 for makingvariable the illumination light quantity distribution in the vicinity ofthe light-source-side focal surface 72 a of the fly eye lens 72. Asectional configuration of each lens element of the other fly eye lensis desirably a regular hexagon rather than a square (rectangle).

FIG. 27 illustrates a configuration adjacent to a wafer stage of theprojection exposure apparatus applied to the respective embodiments ofthis invention. A beam 80A obliquely strikes on an interior of aprojection field region on the wafer 30 in the projection optical system29. Provided is an auto-focus sensor of an oblique incidence systemwhich receives a reflected beam 80B. This focus sensor detects adeviation in the optical-axis direction AX between the surface of thewafer 30 and the best image forming surface of the projection opticalsystem 29. A motor 82 of a Z-stage 81 mounted with the wafer 30 isservo-controlled so that the deviation becomes zero. The Z-stage 81 isthereby moved slightly in the vertical directions (optical-axisdirections) with respect to an XY-stage 83, wherein the exposure isexecuted invariably in the best focus state. In the exposure apparatuscapable of this focus controlling process, the Z-stage 81 is moved withsuch a velocity characteristic as to be controlled in the optical-axisdirections during the exposing process. An apparent focal depth can bethereby further enlarged. This method is attainable by any type ofsteppers on condition that the image side (wafer side) of the projectionoptical system 29 is telecentric.

FIG. 28 shows light quantity (dose) distributions in the optical-axisdirections which are obtained within the resist layers with a movementof the Z-stage 81 during the exposure, or abundance probabilities. FIG.28B shows velocity characteristics of the Z-stage 81 for obtaining thedistribution illustrated in FIG. 28A. Referring to FIGS. 28A and 28B,the axis of ordinate indicates wafer positions in Z-direction(optical-axis direction). The axis of abscissa of FIG. 28A indicates theabundance probability. The axis of abscissa of FIG. 28B indicates avelocity of the Z-stage 81. In the same Figures, a position Zo is thebest focus position.

The abundance probabilities are herein arranged to be substantiallyequal maximal values in two positions +Z1, −Z1 spaced vertically fromthe position Z0 by a theoretical focal depth ±ΔDof of the projectionoptical system 29. In a range from +Z3 to −Z3 therebetween, theabundance probabilities are restrained down to small values. For thispurpose, the Z-stage 81 moves up and down equally at a low velocity V1in the position −Z2 when starting a release of the shutter within theillumination system. Immediately after the shutter has been fullyopened, the Z-stage is accelerated up to a high velocity V2. While theZ-stage 81 moves up and down at the velocity V2, the abundanceprobabilities are restrained down to the small values. Just whenreaching the position +Z3, the Z-stage 81 starts decelerating down tothe low velocity V1. The abundance probability comes to the maximalvalue in the position +Z1. At this moment, a closing command of theshutter is outputted almost simultaneously. The shutter is completelyclosed in the position +Z2.

In this manner, the velocity of the Z-stage 81 is controlled so that theoptical-axis-directional light quantity distributions (abundanceprobabilities) of the exposure quantities imparted to the resist layersof the wafer 30 are arranged to be the maximal values at the two pointsspaced away by approximately a width (2·ΔD₀f) of the focal depth.Although a contrast of the patterns formed on the resist layers is alittle bit reduced, the uniform resolving power can be obtained over awide range in the optical-axis directions.

The above-described cumulative focal point exposure method is applicablein much the same manner to the projection exposure apparatus whichadopts the special illumination method shown in this embodiment. Theapparent focal depth is enlarged by a quantity correspondingsubstantially to a product of an enlarged portion obtained by theillumination method of this invention and an enlarged portion obtainedby the cumulative focal point exposure method. Besides, since thespecial illumination method is adopted, the resolving power itself alsoincreases. For instance, the minimum line width possible to exposure bycombining an i-beam stepper (NA 0.42 of the projection lens) which iscontracted one-fifth that of the prior art with a phase shift reticle,is approximately 0.3 to 0.35 μm. An enlargement rate of the focal depthis about 40% at the maximum. In contrast, the special illuminationmethod according to the present invention is incorporated into thei-beam stepper, and a test is carried out with the ordinary reticle. Asa result, the minimum line width of 0.25˜0.3 μm is obtained. Obtainedalso is much the same enlargement rate of the focal depth as that inusing the phase shift reticle.

A fourth embodiment of the present invention will next be described.FIG. 29 depicts a projection type exposure apparatus (stepper) in thefourth embodiment of this invention. The fly eye lens is divided into aplurality of fly eye lens groups. The light quantity distribution isfocused on each of the fly eye lens groups. The diffraction gratingpattern plate 12 is provided as an optical member (a part of the inputoptical system of this invention) for focusing the light quantitydistribution of the illumination light on each of light-source-sidefocal surfaces 91 a of the fly eye lens groups 91A, 91B. Note that theconstructions toward the light source from the relay lens system 71 andtoward the wafer 30 from the spatial filter 16 are the same as those ofFIG. 20, and the same members are marked with the like symbols.

The diffracted light generated from the diffraction grating patternplate 12 is incident in concentration on each of the fly eye lens groups91A, 91B via the relay lens 73. At this moment, the light-source-sidefocal surfaces 91 a of the fly eye lens groups 91A, 91B and thediffraction grating pattern plate 12 have substantially the Fouriertransform relation through the relay lens 73.

On the other hand, reticle-side focal surfaces 91 b of the fly eye lensgroups 91A, 91B are disposed in an intra-surface direction perpendicularto the optical axis AX so as to coincide substantially with the Fouriertransform plane (pupil conjugate plane) of the reticle patterns 28. Eachof the fly eye lens groups 91A, 91B is independently movable in theintra-surface direction vertical to the optical axis AX and held by amovable member (position adjusting member in the present invention) formaking the lens group movable. The detailed explanation thereof will begiven later.

The individual fly eye lens groups 91A, 91B desirably assume the sameconfiguration and are composed of the same material (refractive index).Respective lens elements of the individual fly eye lens groups 91A, 91Bare double-convex lenses as in the third embodiment. Given therein isthe example where the light-source-side focal surfaces 91 a coincidewith the incident surfaces, and the reticle-side focal surface 91 bcoincide with the exit surface. The fly eye lens elements may notstrictly satisfy this relation but may be plano-convex lenses,convexo-plane lenses or plano-concave lenses. Note that thelight-source-side focal surfaces 91 a of the fly eye lens groups and thereticle-side focal surfaces thereof have, as a matter of course, theFourier transform relation. Hence, in the example of FIG. 29, thereticle-side focal surfaces 91 b of the fly eye lens groups—i.e., theexit surfaces of the fly eye lens groups 91A, 91B—have an image forming(conjugate) relation to the diffraction grating pattern plate 12.

Now, the reticle 27 is illuminated in a homogeneous illuminancedistribution with the luminous fluxes emitted from the reticle-sidefocal surfaces 91 b of the fly eye lens groups 91A, 91B through thecondenser lenses 74, 75 and the mirror 24. In accordance with thisembodiment, the spatial filter 16 is disposed on the exit side of thefly eye lens groups 91A, 91B, thereby cutting off the 0th-orderdiffracted light components from the diffraction grating pattern plate12. The openings of the spatial filter 16 correspond to the respectivepositions of the fly eye lens groups 91A, 91B. For this reason, theillumination light quantity distributions in the vicinity of thereticle-side focal surfaces 91 b of the fly eye lens groups 91A, 91B canbe made zero in portions other than the positions of the fly eye lensgroups 91A, 91B. Therefore, the illumination light with which thereticle patterns 28 are illuminated is limited to the luminous fluxes(from the secondary illuminant images) emitted from the respective flyeye lens groups 91A, 91B. Hence, the luminous fluxes incident on thereticle patterns are limited to those having specific incident angles(plural) thereon.

Note that in the embodiment, each of the fly eye lens groups 91A, 91B ismovable, and the openings of the spatial filter 16 are correspondinglymovable; or alternatively the spatial filter 16 itself has to beexchangeable (the spatial filter 16 will be mentioned later). Theillumination luminous fluxes are diffracted by use of the foregoingdiffraction grating pattern plate 12. The diffracted light componentsare concentrated on the specific positions (fly eye lens groups) withinthe light-source-side focal surfaces of the fly eye lens groups 91A,91B. On this occasion, the concentrated positions are varied dependingon the pitch and the directivity of the diffraction grating patternplate 12. Therefore, the pitch and the directivity of the diffractiongrating pattern plate 12 are determined to concentrate the illuminationlight on the positions of the fly eye lens groups 91A, 91B.

As discussed above, the image of the diffraction grating pattern plate12 is formed on the reticle-side focal surface 91 b of the fly eye lens91. As in the third embodiment described above, however, the reticlepattern surfaces 28 and the reticle-side focal surfaces 91 b of the flyeye lens groups 91A, 91B have the Fourier transform relation. There isno possibility wherein the illumination intensity distribution on thereticle 27 is unhomogenized, or the illuminance homogeneity isdeteriorated.

The diffraction grating pattern plate 12 may, as explained in the thirdembodiment referring to FIG. 21, be not only the transmissive patternplate but also the reflective pattern plate.

If the diffraction grating pattern plate 12 is reflective, asillustrated in FIG. 30, the diffracted light components reflected by thereflective diffraction grating pattern plate 12A are concentrated in thevicinity of the fly eye lens groups 91A, 91B through the relay lens 73.Incidentally, the diffraction grating pattern plate 12 or 12A isexchangeable with a plate having a different pitch so that theillumination light can be concentrated in the vicinity of the respectivefly eye lens groups 91A, 91B even when the individual fly eye lensgroups 91A, 91B move. The diffraction grating pattern plate 12 or 12Amay be rotatable in an arbitrary direction within the surface verticalto the optical axis AX. In this case, however, the Fourier transformrelation between the diffraction grating pattern plate 12 or 12A and thelight-source-side focal surfaces 91 a of the fly eye lens groups 91A,91B should be kept.

By the way, referring to FIG. 29, as in the first embodiment, there areprovided a main control system 58 for generalizing and controlling thedevice, a bar code reader 61, a keyboard 63 and a drive system 92(motor, gear train, etc.) such as movable members for moving the fly eyelens groups 91A, 91B. Registered beforehand in the main control system58 are names of a plurality of reticles dealt with by the stepper andstepper operating parameters corresponding to these names. When the barcode reader 61 reads reticle bar codes BC, the main control system 58outputs, to the drive system 92, the previously registered informationon the moving positions (within the Fourier transform plane) of the flyeye lens groups 91A, 91B as one of the operating parameterscorresponding to the names. The positions of the fly eye lens groups91A, 91B are thereby adjusted to form the optimum light quantitydistributions described in the first embodiment. The operations givenabove can be also executed even by inputting the commands and datadirectly from the keyboard 63.

The optical members (input optical system) are not limited to thediffraction grating pattern plates 12, 12A, these optical members beingintended to concentrate the light quantity distributions over thelight-source-side focal surfaces of the fly eye lens groups 91A, 91B onthe portions in the vicinity of the individual fly eye lens positions.As in the cases shown in FIGS. 22-25 in accordance with the thirdembodiment, the movable plane mirror, the optical fibers, the prism andthe reflection mirror are available.

FIG. 31 shows the case where the movable plane mirror 54 is employed asan input optical system. The constructions toward the light source fromthe relay lens system 71 and toward the reticle from the fly eye lensgroup 91 are the same as those of FIG. 29. The plane mirror 54 isrotated to a plurality of angular positions during the exposure, therebymaking it possible to concentrate the light quantity distributions overthe light-source-side focal surfaces 91 a of the fly eye lens groups91A, 91B on only the portion vicinal to the position of one fly eye lensgroup of the plurality of the fly eye lens groups. Note that when usingthis type of movable plane mirror 54, the relay lens system 73 may beomitted. Further, when each of the fly eye lens groups 91A, 91B moves,angular coordinates of the plurality of angular positions of the planemirror 54 are changed, and the reflected luminous fluxes may beconcentrated in the vicinity of the position of the fly eye lens groupin a new position. Incidentally, the spatial filter 16 illustrated inFIG. 31 is provided on the side of the incident surfaces of the fly eyelens groups 91A, 91B but may be provided on the side of the exitsurfaces as seen in FIG. 29.

FIG. 32 shows a case of using the optical fibers of the input opticalsystem. The exit portions 35A, 35B provided corresponding to the numberof the fly eye lens groups 91A, 91B are constructed integrally with therespective fly eye lens groups in the close proximity to thelight-source-side focal surfaces 91 a of the fly eye lens groups 91A,91B.

The exit portions 35A, 35B (or the lenses between the exit portions 35and the fly eye lens groups 91) are one-dimensionally ortwo-dimensionally movable within the surface vertical to the opticalaxis by means of the drive members such as motors. Even when theindividual fly eye lens groups 91A, 91B are gathered up, theillumination luminous fluxes can be concentrated in the vicinity of theposition of each of the fly eye lens groups after being moved.

FIG. 33 shows a case of employing the prism 33 formed with a pluralityof refractive surfaces as an input optical system. The illuminationlight can be concentrated in the vicinity of each of the fly eye lensgroups 91A, 91B in accordance with a refractive angle of the prism 33 onthe light-source-side focal surfaces 91 a of the fly eye lens groups91A, 91B. Even when the respective fly eye lens groups 91A, 91B move byexchanging the prism 33, the illumination light can be exactlyconcentrated on the position of each of the fly eye lens groups 91A,91B. The device, as a matter of course, incorporates a function toexchange the prism or the like. Where this type of prism is employed,the relay lens system 73 can be omitted.

FIG. 34 shows a case where a plurality of mirrors are used as an inputoptical system. When each of the mirrors 34A-34D is provided with aposition adjusting mechanism and a mechanism for adjusting an angle ofrotation about the optical axis AX, and even after the individual flyeye lens groups 91A, 91B have moved, the illumination luminous fluxescan be focused in the vicinity of the respective fly eye lens groups91A, 91B. A numerical value of the mirrors is not limited. The mirrorsmay be disposed depending on a numerical value of the fly eye lensgroups.

Two groups of the fly eye lenses are provided throughout the fourthembodiment described above, however, three or more groups of the fly eyelenses may be of course provided. Stated also is the optical member forconcentrating the illumination light mainly on the two portions of theindividual fly eye lens groups. The illumination light is, as a matterof course, concentrated on a plurality of positions corresponding to thenumber of the fly eye lens groups. In all the embodiments given above,the illumination light can be concentrated on arbitrary positions(corresponding to the positions of the fly eye lens groups). The opticalmember for concentrating the illumination light on the respective flyeye lens groups is not limited to the types exemplified in theembodiments but may adopt any other types.

Besides, the spatial filter 16 provided in close proximity to thelight-source-side focal surfaces 91 a of the fly eye lenses may beemployed in combination with the respective embodiments shown in FIGS.29 through 34. Spatial filter, 16 can be, though not limited to thereticle-side focal surfaces 91 b and light-source-side focal surfaces 91a of the fly eye lens groups, disposed in arbitrary positions. Forexample, the spatial filter is disposed suitably between theabove-described two focal surfaces 91 a, 91 b.

The optical member for concentrating the illumination light only in thevicinity of the individual fly eye lens groups 91A, 91B is intended toprevent a loss in quantity of the illumination light with which thereticle 27 is illuminated. The optical member is not associated directlywith the constitution for obtaining the effects of the high resolvingpower and large focal depth that are characteristic of the projectiontype exposure apparatus according to the present invention. Hence, theoptical member may be only a lens system having a diameter large enoughto make the illumination light incident in flood on each of the fly eyelens groups after being adjusted in terms of position.

As in the construction, depicted in FIG. 26, of the third embodiment,the spatial filter 16A may be provided, or a variable field stop 76 mayalso be provided as in the same way with the third embodiment. Thespatial filter 16A is placed on the reticle-side focal surface 91 b ofthe fly eye lens group 91 or in the vicinity of the conjugate surfacethereof, thereby regulating the illumination luminous fluxes emergingfrom the fly eye lens groups 91A, 91B. Note that if there is a systemcapable of focusing the illumination luminous fluxes incident on the flyeye lens groups 91A, 91B only thereon effectively, the spatial filter 16may not be provided on the reticle-side focal surface 91 b or in thevicinity of the conjugate surface thereof.

For satisfying the condition of the σ-value (0.1≦σ≦0.3) determined byone of the fly eye lens groups, a magnitude (in the intra-surfacedirection vertical to the optical axis) of the exit end areas of each ofthe fly eye lens groups 91A, 91B may be determined to match with theillumination luminous fluxes (exit luminous fluxes).

A variable aperture stop (equivalent to the spatial filter 16) isprovided in the vicinity of the reticle-side focal surface 91 b of eachof the fly eye lens groups 91A, 91B, and the numerical aperture of theluminous flux from each of the fly eye lens groups is made variable,thus changing the σ-value. Correspondingly, the variable aperture stop(NA regulating stop) is disposed close to the pupil (incident pupil orexit pupil) 51 of the projection optical system 29, thereby furtheroptimizing the σ-value with respect to NA in the projection system.

The illumination of the luminous fluxes incident on the respective flyeye lens groups expands to some extent outwardly of the incident endsurfaces of the fly eye lens groups. Besides, if the distributions inquantity of the light incident on the respective fly eye lens groups areuniform, the illuminance homogeneity on the reticle pattern surfaces canbe preferably further enhanced.

Next, an embodiment of the movable portions for making the fly eye lensgroups movable will be explained in conjunction with FIGS. 35 and 36.

FIG. 35 is a diagram illustrating the movable portions viewed from theoptical-axis direction. FIG. 36 is a diagram showing the same viewedfrom the direction vertical to the optical axis.

A plurality of, i.e., four fly eye lens groups 91A, 91B, 91C, 91D aredisposed at substantially equal distances from the optical axis in FIG.35. Each of the fly eye lens groups 91A, 91B, 91C, 91D is, asillustrated in FIG. 35, composed of, though not limited to this, 32pieces of lens elements. In an extreme case, the fly eye lens group maybe constructed of one lens element. Now, turning to FIGS. 35 and 36, thefly eye lens groups 91A, 91B, 91C, 91D are held by jigs 103 a, 103 b,103 c, 103 d. These jigs 103 a, 103 b, 103 c, 103 d are furthersupported on movable members 101 a, 101 b, 101 c, 101 d through supportbars 100 a, 100 b, 100 c, 100 d. These support bars 100 a, 100 b, 100 c,100 d are stretchable and contractible in the optical-axis directionwith the aid of drive elements such as motors and gears incorporatedinto the movable members 101 a, 101 b, 101 c, 101 d. The movable members101 a, 101 b, 101 c, 101 d themselves are movable along fixed guides 102a, 102 b, 102 c, 102 d. The individual fly eye lens groups 91A, 91B,91C, 91D are therefore independently movable in the intra-surfacedirection perpendicular to the optical axis.

Respective positions (within the surface vertical to the optical axis)of the fly eye lens groups 91A, 91B, 91C, 91D depicted in FIG. 36 aredetermined (changed) preferably depending on the reticle patterns to betransferred.

The optimum positions of the respective fly eye lens groups are setunder the same conditions as those explained referring to FIGS. 14 and15 in the first embodiment.

A concrete example of the positional determination of each of the flyeye lens groups is the same as the determining method explained in thefirst embodiment with reference to FIGS. 14 and 15. It is assumed thatthe central position (the optimum position of the gravity of the lightquantity distribution of the secondary illuminant image which is createdby each of the fly eye lens groups) of each of the fly eye lens groupsis, as illustrated in FIG. 15B, on the Y-directional line segment Lαpresumed within the Fourier transform plane. Alternatively, it isassumed that the center of each of the fly eye lens groups is placed onan arbitrary position on the line segment Lβ, or, as illustrated in FIG.15D, on the line segments Lα, Lβ defined such as α=β=f·(1/2)·(λ/Px) oron the line segments Lγ, Lε defined such as γ=ε=f·(1/2)·(λ/Py). Based onthese assumptions, the focal depth can be maximized. As in the firstembodiment, the 0th-order diffracted light component Do coining from thereticle patterns 28 and any one of the (+) primary diffracted lightcomponent Dp and the (−) primary diffracted light component Dm may bearranged to pass through light paths having the equal distances from theoptical axis AX on the pupil surface 51 within projection optical system29. If the reticle patterns 28, as seen in FIG. 15D, contain thetwo-dimensional periodic patterns, and when paying attention to onespecific 0th-order diffracted light component, there probably existorder diffracted light components including the primary diffracted lightcomponents of which the order is higher than the 0th-order diffractedlight component, which are distributed in the X-direction (the firstdirection) and in the Y-direction (the second direction) about thesingle 0th-order diffracted light component on the pupil surface 51 ofthe projection optical system. Supposing that the image of thetwo-dimensional patterns is formed well with respect to one specific0th-order diffracted light component, the position of the specific0th-order diffracted light component may be adjusted so that three lightcomponents i.e., one of the higher-order diffracted light componentsdistributed in the first direction, one of the higher-order diffractedlight components distributed in the second direction and one specific0th-order diffracted light component are distributed at substantiallyequal distances from the optical axis AX on the pupil plane 51 of theprojection optical system. For instance, the central position of theexit portion in FIG. 15D is arranged to coincide with any one of pointsPξ, Pη, Pκ, Pμ. The points Pξ, Pη, Pκ, Pμ are all intersections of theline segment Lα or Lβ (the optimum position to the X-directionalperiodicity, i.e., the position in which the 0th-order diffracted lightcomponent and one of the (±) primary diffracted light components in theX-direction have substantially equal distances from the optical axis onthe pupil surface 51 of the projection optical system) and line segmentsLγ, Lε (the optimum positions to the Y-directional periodicity).Therefore, those positions are the light source positions optimal toeither the pattern direction X or the pattern direction Y.

Note that in this embodiment, an arbitrary light quantity distributioncan be, as in the first embodiment, formed on the Fourier transformplane by controlling the luminous flux transform member and the movableoptical member on the basis of the information of bar codes and thelike. In this case, the fly eye lens groups 91A to 91D are disposed notonly discretely but also integrally about the optical axis, whereby achangeover to the ordinary illumination can be performed.

A light scattering member such as a diffusion plate and an optical fiberbundle are provided in close proximity to the light-source-side focalsurface 91 a of the fly eye lens 91, thereby homogenizing theillumination light. Alternatively, the illumination light may behomogenized by employing an optical integrator such as a further fly eyelens (hereinafter referred to as the other fly eye lens) separately fromthe fly eye lens 72 used in the embodiments of the present invention. Atthis time, the other fly eye lens is disposed preferably closer to thelight source (lamp) 1 than the optical member e.g., the diffractiongrating pattern plate 12 or 12A shown in FIGS. 29 and 30 for makingvariable the illumination light quantity distribution in the vicinity ofthe light-source-side focal surface 91 a of the fly eye lens 91. Asectional configuration of each lens element of the other fly eye lensis desirably a regular hexagon rather than a square (rectangle). In thiscase, the σ-value may be made variable by making the numerical apertureof the illumination system variable while providing an aperture stop onthe reticle-side focal surface of the other fly eye lens. Further, theσ-value may be also made variable by changing a magnitude of theluminous flux incident on the other fly eye lens while providing a zoomlens (afocal zoom lens) on the light path leading from the light sourceup to the other fly eye lens.

Given above is the example of determining the positions of the pluralityof fly eye lens groups. The illumination luminous fluxes areconcentrated corresponding to the moving positions of the respective flyeye lens groups by means of the foregoing optical members (thediffraction grating pattern plate, the movable mirror, the prism or thefibers). The optical member for this concentrating process may not beprovided.

The luminous fluxes emitted from the fly eye lens groups are incidentobliquely on the reticle. If a direction of the light quantity gravityof the (plural) incident luminous fluxes inclined thereto is notperpendicular to the reticle, there arises a problem in which a positionof the transferred image shifts in the intra-surface direction of thewafer during minute defocusing of the wafer 30. In order to prevent thisshift, the direction of the light quantity gravity of the (plural)illumination luminous fluxes from the fly eye lens groups is keptvertical to the reticle patterns, viz., parallel to the optical axis AX.

More specifically, on the assumption that the optical axis (centralline) is set in the respective fly eye lens groups, it may be sufficientto make zero a vector sum of a product of the intra Fourier transformplane positional vector of the optical axis (central line) on the basisof the optical axis AX of the projection optical system 29 and aquantity of light emitted from each of the fly eye lens groups. Aneasier method is that 2m-groups (m is the natural number) of fly eyelenses are provided; positions of m-groups of the fly eye lenses aredetermined by the optimizing method described above; and remainingm-groups and the former m-groups of fly eye lenses are disposed insymmetry with respect to the optical axis AX.

If the device further includes n-groups (n is the natural number), andwhen the number of groups of the fly eye lenses is set to m smaller thann, the remaining (n−m) groups of fly eye lenses may not be used. Toeliminate the use of the (n−m) groups of fly eye lenses, the spatialfilter 16 may be provided on the positions of (n−m) groups of fly eyelenses. At this time, the optical member for concentrating theillumination light on the positions of (n−m) groups of fly eye lensespreferably does not concentrate the light on the (n−m) groups of fly eyelenses.

The positions of openings of the spatial filter 16 are desirablyvariable corresponding to the movements of the fly eye lens groups.Alternatively, there is provided a mechanism for exchanging the spatialfilter, 16 in accordance with the positions of the respective fly eyelenses. The device may incorporate some kinds of light shieldingmembers.

As depicted in FIG. 36, each of the jigs 103 a, 103 b, 103 c, 103 d forholding the respective fly eye lens groups 91A, 91B, 91C, 91D has lightshielding blades 104 a, 104 b. In this case, the opening of the spatialfilter 16 may be formed considerably larger than the diameter of the flyeye lens. Hence, one spatial filter 16 is capable of corresponding tothe positions of a variety of fly eye lenses. If the light shieldingblades 104 a, 104 b deviate slightly in the optical-axis direction, aconstraint given to the moving range of the fly eye lens groups isreduced.

Light scattering members such as diffusion plates and optical fibers areemployed in the vicinity of the light-source-side focal surfaces 91 a ofthe fly eye lens groups 91A, 91B, 91C, 91D, thereby homogenizing theillumination light.

A fifth embodiment will be next explained. Provided in this embodimentis a holding member for integrally holding the plurality of fly eye lensgroups. The fly eye lens groups held in the optimum placement areselectable by driving the holding member.

FIG. 37 illustrates a construction of the projection type exposureapparatus in the fifth embodiment of the present invention. Thediffraction grating pattern plate 12 is given as an optical member (apart of the input optical system) for concentrating the light quantitydistributions of the illumination light on the light-source-side focalsurfaces of the fly eye lens groups. Note that the same members as thosein FIG. 29 are marked with the like symbols.

A holding member 111 integrally holds fly eye lens groups 111A, 111B sothat the center (in other words, the gravity of the each of the lightquantity distributions created by the secondary illuminant images in therespective fly eye lens groups 111A, 111B) of each of the fly eye lensgroups 111A, 111B is set in a discrete position eccentric from theoptical axis AX by a quantity determined depending on the periodicity ofthe reticle patterns. Fixed integrally to a movable member 112(switching member in this invention) together with the holding member111 are a plurality of holding members (not illustrated) for holding theplurality of fly eye lens groups while making their eccentric statesrelative to the optical axis AX different from each other in accordancewith a difference in terms of the periodicity of the reticle patterns28. This movable member 112 is driven, with the result that theplurality of holding members can be so disposed in the light path of theillumination optical system as to be individually exchangeable. Thedetailed description thereof will be given later.

Each of the plurality of fly eye lens groups (111A, 111B) fixed by thesame holding member desirably assumes the same configuration and iscomposed of the same material (refractive index). In this embodiment,the holding members (fly eye lens groups 111A, 111B) are exchangeable,and hence the openings of the spatial filter 16 have to be variablecorrespondingly; or alternatively, the spatial filter 16 has to be alsoexchangeable. For instance, the spatial filter 16 is fixed to theholding member together with the fly eye lens groups 111A, 111B, anddesirably they are arranged to be integrally exchangeable. Note that amagnitude (thickness) of the luminous flux incident on each of the flyeye lens groups 111A, 111B is set equal to or smaller than a magnitudeof each of the light-source-side focal surfaces 111 a of the fly eyelens groups 111A, 111B. In this case, the spatial filter 16 is notparticularly, as a matter of course, provided in the illuminationoptical system (in the vicinity of the fly eye lens groups).

The diffraction grating pattern plate 12 or 12A may be rotatable in anarbitrary direction within the surface vertical to the optical axis AX.With this arrangement, it is possible to correspond to such a case thatthe pitch direction of the line-and-space patterns of the reticlepatterns 28 is different from the directions X, Y (i.e., the fly eyelens groups 111A, 111B move in the pitch direction (rotate about theoptical axis AX)).

Provided according to this embodiment, as in the fourth embodiment, themain control system 58 for generalizing and controlling the device, thebar code reader 61, the keyboard 63 and the drive system (motor, geartrain, etc.) 113 of movable members for moving the fly eye lens groups111A, 111B. Registered beforehand in the main control system 58 arenames of a plurality of reticles dealt with by the stepper and stepperoperating parameters corresponding to the names. Then, the main controlsystem 58 outputs, when the bar code reader 61 reads the reticle barcodes BC, a predetermined drive command to the drive system 113 byselecting one of the plurality of holding members which matches bestwith the previously registered information (corresponding to theperiodicity of the reticle patterns) on the positions (within the pupilconjugate surface) of the fly eye lens groups 111A, 111B as one of theoperating parameters corresponding to the names thereof. The fly eyelens groups 111A, 111B held by the previously selected holding memberare thereby set in the positions on Lα, Lβ shown in FIG. 15B and thepositions on Lα, Lβ, Lγ,Lε (especially the positions on Pξ, P^(n), Pχ,Pμ) shown in FIG. 15D in the first embodiment. The operations describedabove are executable even by the operator's inputting the commands andthe data from the keyboard 63 directly to the main control system 58.

The optical member (input optical system) is not limited to thetransmissive diffraction grating pattern plate 12, this optical memberbeing intended to concentrate the light quantity distributions over thelight-source-side focal surfaces of the fly eye lens groups in thevicinity of the positions of the individual fly eye lenses. As explainedin the fourth embodiment with reference to FIGS. 30-34, the reflectivediffraction grating pattern plate 12A, the movable plane mirror 54, theoptical fibers 35, the prism 33 and the plurality of reflection mirrors34 may be provided in place of the diffraction grating pattern plate 12.Additionally, the diffraction grating pattern plates 12, 12A and theprism 33 are replaced; or a plurality of angular position coordinates ofthe movable plane mirror 54 are changed; or the exit portions of theoptical fibers are made movable; or each of the reflection mirrors isprovided with the position adjusting mechanism and the mechanism foradjusting the angle of rotation about the optical axis AX. With thesearrangements, if the fly eye lens groups move with the replacement ofthe holding member, the illumination luminous fluxes can be concentratedin the vicinity of the positions of the respective fly eye lens groupsafter being moved.

As in the fourth embodiment, the spatial filter 16, may be disposed inthe light-source-side focal surface 111 a of the fly eye lens or used incombination with the above. The placement of the spatial filter is notlimited to the light-source-side focal surfaces 111 b and thereticle-side focal surfaces 111 a of the fly eye lens groups but may bedisposed in arbitrary positions. Further, the optical member (inputoptical system) for concentrating the illumination light only in thevicinity of the individual fly eye lens groups 111A, 111B may be only alens having a diameter large enough to make the illumination lightincident in flood on each of the plurality of fly eye lens groups.

As explained in the fourth embodiment in conjunction with FIG. 26, thespatial filter 16A and the field stop may be provided.

Next, a construction of the movable member 112 (switching member in thepresent invention) for exchanging the holding member will be describedreferring to FIGS. 38 and 39.

FIG. 38 shows a concrete construction of the movable member. Four piecesof holding members 111, 114, 115, 116 are herein disposed at intervalsof approximately 90 degrees on the movable member (turret plate) 112rotatable about a rotary axis 112 a. FIG. 38 illustrates a situation inwhich illumination luminous fluxes ILa, ILb (dotted lines) are incidenton the respective fly eye lens groups 111A, 111B; and the holding member111 is disposed in the illumination optical system. At this time, theholding member 111 is placed in the illumination optical system so thatthe center of this member coincides substantially with the optical axisAX. The plurality of fly eye lens groups 111A, 111B are held integrallyby the holding member 111 so that the centers of these lens groups areset in discrete positions eccentric from the optical axis AX of theillumination optical system by a quantity determined depending on theperiodicity of the reticle patterns. These lens groups are placedsubstantially in symmetry with respect to the center (optical axis AX)of the holding member 111.

Now, each of the four holding members 111, 114, 115, 116 holds theplurality of fly eye lens groups while making their eccentric states(i.e., positions within the surface substantially perpendicular to theoptical axis AX) from the optical axis AX (center of the holding member)different from each other in accordance with a difference in terms ofthe periodicity of the reticle patterns 28. Both of the holding members111, 114 have two fly eye lens groups (111A, 111B) and (114A, 114B).These fly eye lens groups are, when being disposed in the illuminationoptical system, fixed so that their array directions are substantiallyorthogonal to each other. The holding member 115 places and fixes thefour fly eye lens groups 115A-115D substantially at equal distances fromthe center 115 cA (optical axis AX) thereof. In accordance with thisembodiment, the holding member 116, which fixes one fly eye lens group116A substantially at the center, is used for effecting the exposurebased on a known method.

As is obvious from FIG. 38, the turret plate 112 is rotated by the driveelement 113 consisting of a motor and a gear, as stated earlier, inaccordance with the information of the reticle bar codes BC. The fourholding members 111, 114, 115, 116 are thereby exchanged, and thedesired holding member corresponding to the periodicity (pitch, arraydirection, etc.) of the reticle patterns can be disposed in theillumination optical system.

Selected, as discussed above, in accordance with the information of thereticle bar codes BC is whether to effect either the known exposure forforming the light quantity distributions substantially about the opticalaxis on the Fourier transform plane or the exposure by the inclinedillumination light explained in this embodiment. In the case ofperforming the known exposure, the holding member 116 is selected. Inthe case of performing the exposure based on the inclined illuminationlight, any one of the holding members 111, 114, 115 may be selected.When executing the known exposure, and if the holding member 116 isselected, it is required that the input optical system be exchanged foreffecting the illumination as it used to be done. If the illuminationlight can be concentrated through the lens 71 on the fly eye lens group116A, the input optical system such as fibers, retreats from within thelight path.

In each of the four holding members, the plurality of fly eye lensgroups are herein fixed in a predetermined positional relation, andhence there is no necessity for performing the positional adjustmentbetween the plurality of fly eye lens groups when exchanging the holdingmember. Therefore, positioning of the holding members as a whole may beeffected with respect to the optical axis AX of the illumination opticalsystem. Consequently, there is produced such an advantage that noprecise positioning mechanism is needed. At this time, the drive element113 is used for the positioning process, and it is therefore desirableto provide a rotary angle measuring member such as, e.g., a rotaryencoder. Note that each of the plurality of fly eye lens groupsconstituting the holding members comprises, as shown in FIG. 38, 16pieces of lens elements (only the fly eye lens group 116A is composed of36 pieces lens elements). The numerical number is not limited to this.In an extreme case, the fly eye lens group consisting of one lenselement may also be available.

Referring to FIG. 37, the spatial filter 16 is disposed in rear(reticle-side) of the holding member 111. In each of the holdingmembers, when the portions other than the fly eye lens groups are formedas light shielding portions, the spatial filter 16 is not particularlyprovided. At this time, the turret plate 112 may be a transmissiveportion or a light shielding portion. The number of the holding membersto be fixed to the turret plate 112 and the eccentric states (positions)of the plurality of fly eye lens groups are not limited to those shownin FIG. 38 but may be arbitrarily set corresponding to the periodicityof the reticle patterns to be transferred. If there is a necessity forstrictly setting the incident angles and the like of the illuminationluminous fluxes on the reticle patterns, each of the plurality of flyeye lens groups may be so constructed as to be minutely movable in theradial directions (radiant directions) about the optical axis AX in theholding member. Further, the holding members (fly eye lens groups 111A,111B) may be so constructed as to be rotatable about the optical axisAX. On this occasion, if especially the optical fiber bundle 35 isemployed as an optical member (input optical system) for concentratingthe illumination luminous fluxes in the vicinity of each of theplurality of fly eye lens groups, the exit ends 35A, 35B thereof arearranged to move with movements of the fly eye lens groups. Forinstance, the exit ends 35A, 35B and the fly eye lens groups may beintegrally fixed. In addition, the rectangular fly eye lens groups arerelatively inclined with rotation of the holding member. However, whenrotating the holding member, it is desirable that only the positions ofthe fly eye lens groups are moved without causing the above-mentionedinclination.

When exchanging the holding member, it is necessary to exchange theinput optical system such as, e.g., the diffraction grating patternplate 12, the relay lens 73 (FIG. 37) and the optical fiber bundle 35.Desirably, the input optical systems corresponding to the eccentricstates of the plurality of fly eye lens groups are integrallyconstructed for every holding member and fixed to the movable member112.

FIG. 39 is a diagram showing a variant form of the movable member forexchanging the holding member. The input optical system (optical fiberbundles 117, 118) and the holding members (122, 124) are integrallyfixed to the movable member (support bar 125). It is permitted that theabove-described other optical systems, though the optical fiber bundleis exemplified herein, may be employed as an input optical system.Incidentally, the fundamental construction (the example where theoptical fiber bundle is used as an input optical system) has beenalready explained in the fourth embodiment (FIG. 32) and thereforetouched briefly herein.

Referring to FIG. 39, the two fly eye lens groups 119A, 119B areintegrally held by the holding member 122, while an incident portion 117a and an exit portion 117 b of the optical fiber bundle 117 are bothheld by a fixing tool 123. At the same moment, the holding member 122 isintegrally fixed to the fixing tool 123. Excepting the fly eye lensgroups 119A, 119B, the light shielding portions (the illustrated obliqueline portions corresponding to, e.g., the spatial filter 16 of FIG. 37)occupy the interior of the holding member. On the other hand, the flyeye lens groups 121A, 121B for the replacement are integrally held bythe holding member 124. An incident portion 118 a and an exit portion118 b of an optical fiber bundle 118 are both held by a fixing tool 125.Simultaneously, the holding member 124 is integrally fixed to the fixingtool 125. As in the same way described above, the interior of theholding member 124 is formed with the light shielding portions. Further,the fixing tools 123, 125 are connectively fixed by means of aconnecting member 127. Therefore, the holding members may be exchangedfor every fixing tool. Note that in FIG. 39, the fixing tool 123(holding member 122) exists in the illumination optical system, whereasthe fixing tool 125 for the replacement is set in a position deviatingfrom the illumination optical system. The constructions toward the lightsource from the relay lens system 71 and toward the reticle from thecondenser lens 74 are the same as those shown in FIG. 37.

By the way, the holding member is exchanged by pushing or pulling thesupport bar 129 with the help of the drive element 128. Hence, asillustrated in FIG. 39, when exchanging the holding member, the fly eyelens groups and the optical fiber bundle are so arranged as to beintegrally exchangeable. With this arrangement, it may be sufficientthat the fore-going integral member groups (fixing tools) are matched inposition with the illumination optical system as. a whole. Produced isan advantage of eliminating the necessity for effecting the positionaladjustments between the respective members (fly eye lens groups, opticalfiber bundle, etc.) per exchanging process. At this time, the driveelement 128 is employed also for positioning. It is therefore desirableto provide a position measuring member such as, for example, a linearencoder, a potentiometer, etc.

Note that the number of the fly eye lens groups per holding member shownin FIGS. 38 and 39 and the number of the lens elements constituting thefly eye lens groups may be arbitrarily set. Besides, the configurationsof the fly eye lens group and of the incident or exit surface of thelens element are not limited to the rectangle.

Now, the respective positions of the plurality of fly eye lens groupsdepicted in FIGS. 38 and 39 in other words, the holding member to beselected are preferably determined (changed) depending on the reticlepatterns to be transferred. A method of determining (selecting) thepositions of the respective fly eye lens groups is the same with thefourth embodiment (the method being identical with that explained in thefirst embodiment). To be more specific, the holding member including thefly eye lens group may be disposed in the incident position (incidentangle) or in the vicinity thereof on the reticle patterns to obtain theeffects given by the improved optimum resolving power and focal depth tothe degree of fineness (pitch) of the patterns to be transferred usingthe illumination luminous fluxes coming from the respective fly eye lensgroups.

It is to be noted that the openings of the spatial filter 16 aredesirably variable corresponding to the movements of the respective flyeye lens groups with the exchange of the holding member. Providedalternatively is a mechanism for exchanging the spatial filter 16 inaccordance with the positions of the individual fly eye lenses. Besides,the device may incorporate some kinds of light shielding members.

In the embodiment discussed above, the premise is that the plurality ofholding members (fly eye lens groups) are so constructed as to beexchangeable. According to the present invention, as a matter of course,the holding members are not necessarily so constructed as to beexchangeable. For instance, only the holding member 111 depicted in FIG.38 is merely disposed in the illumination optical system. With thisarrangement, there can be of course attained the effects (to actualizethe projection type exposure apparatus exhibiting the high resolvingpower and large focal depth) of the present invention. Incidentally, ifit is permitted to cause somewhat a loss in the illumination lightquantity from the light source, the optical member (input opticalsystem) for concerning the illumination luminous fluxes on the fly eyelens groups is not particularly disposed.

In this embodiment also, the other fly eye lens may be also provided.The σ-value determined by one if the respective fly eye lens groups isset to preferably 0.1 through 0.3.

The cumulative focal point exposure method described in the thirdembodiment is, though the first to fifth embodiments have been describedso far, applicable to the first, second, fourth and fifth embodiments.

In the first through fifth embodiments discussed above, the explanationshave been given by use of the mercury lamp 1 as a light source. Thelight source may include, however, other bright-line lamps and lasers(excimers, etc.); or a continuous spectrum light source is alsoavailable. A large proportion of the optical members in the illuminationoptical system are composed of lenses. However, mirrors (concave andconvex mirrors) are also available. The projection optical system may bea refractive system or reflective system or reflective/refractivesystem. In the embodiments, the double-side telecentric system is used.However, a one-side telecentric system or non-telecentric system is alsoavailable. If the correction of the chromatic aberration of each opticalsystem is insufficient, a band-pass filter and a dichroic mirrorintervene in the light path of the illumination system to utilize onlythe monochromatic light.

Although illustrative embodiments of present invention have beendescribed in detail with reference to the accompanying drawings, it isto be understood that the present invention is not limited to thoseembodiments. Various changes or modifications may be effected therein byone skilled in the art without departing from the scope or spirit of theinvention.

What is claimed is:
 1. A projection exposure apparatus comprising: anillumination optical system having at least two optical integratorsseparated from each other, of which exit surface are arranged on a sameplane perpendicular to an optical axis of the illumination opticalsystem to illuminate a mask with light from a secondary light sourceformed by one of the at least two optical integrators; and a movablemember that holds the at least two optical integrators so that adistribution of the secondary light source is defined by the one of theat least two optical integrators selected in accordance with a patternformed on the mask.
 2. An apparatus according to claim 1, furthercomprising a driving member connected with said movable member to changepositions of said at least two optical integrators on said same plane.3. A projection exposure apparatus comprising: an illumination systemhaving a plurality of optical integrators that form different secondarylight sources of which distributions are different from each other toilluminate a mask with light from a secondary light source selectedbased on a pattern formed on the mask and a holding member that holdsthe plurality of optical integrators so that one of the plurality ofoptical integrators that form the selected secondary light source isdisposed in an optical path of the illumination system; and a projectionoptical system disposed between the mask and a substrate to projectlight from the illuminated mask onto the substrate.
 4. An apparatusaccording to claim 3, wherein at least one of said secondary lightsources has a decreased intensity distribution within a portionincluding an optical axis of said illumination system.
 5. An apparatusaccording to claim 3, wherein at least one of said secondary lightsources has a decreased intensity distribution within a portion definedalong orthogonal first and second directions.
 6. An apparatus accordingto claim 3, wherein said illumination system includes and a drivingmember connected with the holding member so that each of said opticalintegrators is selectively disposed in a light path of said illuminationsystem.
 7. An apparatus according to claim 3, wherein said illuminationsystem includes an equal number of a plurality of input optical devicesas a number of said optical integrators so that each of the plurality ofinput optical devices directs light from a light source to a separateone of said optical integrators.
 8. An apparatus according to claim 3,wherein said plurality of optical integrators includes a firstintegrator having four off-axis fly-eye lenses separated from each otherand a second integrator having an on-axis fly-eye lens.
 9. A projectionexposure apparatus comprising: a light source; an optical integratordisposed between the light source and a mask; a condensing opticalsystem disposed between the optical integrator and the mask to irradiateon the mask light from a secondary light source formed by the opticalintegrator; a projection system disposed between the mask and asubstrate to project light irradiated on the mask onto the substrate; alight shielding device disposed between the light source and thecondensing optical system to provide the secondary light source with adecreased intensity portion defined along first and second directions inwhich linear features formed on the mask extend; and a diffractionoptical element disposed between the light source and the lightshielding device to generate diffracted light incident on a portiondifferent from the decreased intensity portion in the secondary lightsource, with light from the light source.
 10. An apparatus according toclaim 9, wherein said optical integrator includes a fly-eye lens, saidlight shielding device being disposed between the fly-eye lens and saidcondensing optical system.
 11. A projection exposure apparatuscomprising: an illumination system that illuminates a pattern with lightfrom four off-axis secondary light sources formed with light from alight source and defined by a light shielding device, said illuminationsystem including a diffraction optical element disposed between thelight source and the light shielding device to generate diffracted lightincident on a portion including areas in which the four off-axissecondary light sources are formed with light from the light source; anda projection optical system that projects an image of the pattern on apredetermined plane, wherein a ratio of a numerical aperture of a lightbeam from each of said four secondary light sources to a numericalaperture of said projection optical system is substantially 0.1 through0.3.
 12. A projection exposure apparatus comprising: a light source; afirst optical system that selectively forms different secondary lightsources of different light intensity distributions with light from saidlight source; a second optical system that illuminates a pattern withlight from a secondary light source selectively formed by said firstoptical system based on the pattern; a projection system that projectsan image of said pattern on a predetermined plane; a plurality of inputoptical devices that form different distributions from each other oflight incident on said first optical system to provide light incident onsaid first optical system with an intensity distribution selected basedon a secondary light source formed by said first optical system; and aholding member that holds said plurality of input optical devices sothat one of said plurality of input optical devices to form saidselected intensity distribution is disposed between said light sourceand said first optical system.
 13. An apparatus according to claim 12,wherein said first optical system includes a plurality of opticalintegrators that form said different secondary light sources and amovable member that holds the plurality of optical integrators so thateach of the plurality of optical integrators is selectively disposedbetween said plurality of input optical devices and said second opticalsystem.
 14. An apparatus according to claim 12, wherein said firstoptical system forms a secondary light source having a decreasedintensity distribution within a portion including an optical axisthereof or within a portion defined along first and second directions.15. A method of exposing a substrate with a pattern on a mask, themethod comprising the steps of: arranging one of a plurality of opticalintegrators that form different secondary light sources of differentlight intensity distributions in an optical path of an illuminationsystem, each of the secondary light sources having a differentdistribution, the illumination system illuminating the pattern withlight from a secondary light source formed by the arranged one of theplurality of optical integrators, the arranged one of the opticalintegrators being arranged based on the pattern; and projecting an imageof the pattern on the substrate.